Author: "Institut für Astrophysik [Göttingen]" - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"Institut für Astrophysik [Göttingen]"' showing total 90 results

Start Over Author "Institut für Astrophysik [Göttingen]"

90 results on '"Institut für Astrophysik [Göttingen]"'

1. Imaging individual active regions on the Sun's far side with improved helioseismic holography

Author: Dan Yang, Laurent Gizon, Hélène Barucq, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Modélisation et simulation de la propagation des ondes fondées sur des mesures expérimentales pour caractériser des milieux géophysiques et héliophysiques et concevoir des objets complexes (MAKUTU), Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Polytechnique de Bordeaux (Bordeaux INP), NYUAD Center for Space Science, New York University [Abu Dhabi], NYU System (NYU)-NYU System (NYU), Institut für Astrophysik [Göttingen], and Georg-August-University = Georg-August-Universität Göttingen
Subjects: [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Sun: activity, FOS: Physical sciences, Astronomy and Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR), Sun: helioseismology
Abstract: Helioseismic holography is a useful method to detect active regions on the Sun's far side and improve space weather forecasts. We aim to improve helioseismic holography by using a clear formulation of the problem, an accurate forward solver in the frequency domain, and a better understanding of the noise properties. Building on the work of Lindsey et al., we define the forward- and backward-propagated wave fields (ingression and egression) in terms of a Green's function. This Green's function is computed using an accurate forward solver in the frequency domain. We analyse overlapping segments of 31 hr of SDO/HMI dopplergrams, with a cadence of 24 hr. Phase shifts between the ingression and the egression are measured and averaged to detect active regions on the far side. The phase maps are compared with direct EUV intensity maps from STEREO/EUVI. We confirm that medium-size active regions can be detected on the far side with high confidence. Their evolution (and possible emergence) can be monitored on a daily time scale. Seismic maps averaged over 3 days provide an active region detection rate as high as 75% and a false discovery rate only as low as 7%, for active regions with areas above one thousandth of an hemisphere. For a large part, these improvements can be attributed to the use of a complete Green's function (all skips) and to the use of all observations on the front side (full pupil). Improved helioseismic holography enables the study of the evolution of medium-size active regions on the Sun's far side., 15 pages, 14 figures
Published: 2023
Full Text: View/download PDF

2. Central kinematics of the Galactic globular cluster M80

Author: Stefan Dreizler, Benjamin Giesers, Peter M. Weilbacher, Fabian Göttgens, Sebastian Kamann, Mark den Brok, Tim-Oliver Husser, Romain Fétick, Holger Baumgardt, Davor Krajnović, Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Astrophysics Research Institute [Liverpool] (ARI), Liverpool John Moores University (LJMU), School of Mathematics and Physics [Brisbane], University of Queensland [Brisbane], Leibniz-Institut für Astrophysik Potsdam (AIP), DOTA, ONERA, Université Paris Saclay [Châtillon], ONERA-Université Paris-Saclay, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), FG, SD, BG, and TOH acknowledge funding from the Deutsche Forschungsgemeinschaft (grant DR 281/35-1 and KA 4537/2-1) and from the German Ministry for Education and Science (BMBFVerbundforschung) through grants 05A14MGA, 05A17MGA, 05A14BAC, 05A17BAA and 05A20MGA. SK gratefully acknowledges funding from UKRI in the form of a Future Leaders Fellowship (grant no. MR/T022868/1). The authors acknowledge the French National Research Agency (ANR) for supporing this work through the ANR APPLY (grant ANR-19-CE31-0011) coordinated by B. Neichel. The work was supported by the North-German Supercomputing Alliance (HLRN)., and ANR-19-CE31-0011,APPLY,Prédiction de la réponse impulsionnelle pour les obervations assitées par Optique Adaptative(2019)
Subjects: FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Stellar kinematics, [SPI]Engineering Sciences [physics], Globular clusters, 0103 physical sciences, Cluster (physics), Astrophysics::Solar and Stellar Astrophysics, Surface brightness, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), QC, Astrophysics::Galaxy Astrophysics, Stellar dynamics, QB, Physics, [PHYS]Physics [physics], Solar mass, 010308 nuclear & particles physics, Velocity dispersion, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Imaging spectroscopy, Black hole, Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Globular cluster, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics
Abstract: We use spectra observed with the integral-field spectrograph MUSE to reveal the central kinematics of the Galactic globular cluster Messier 80 (M80, NGC 6093). Using observations obtained with the recently commissioned narrow-field mode of MUSE, we are able to analyse 932 stars in the central 7.5 arcsec by 7.5 arcsec of the cluster for which no useful spectra previously existed. Mean radial velocities of individual stars derived from the spectra are compared to predictions from axisymmetric Jeans models, resulting in radial profiles of the velocity dispersion, the rotation amplitude, and the mass-to-light ratio. The new data allow us to search for an intermediate-mass black hole (IMBH) in the centre of the cluster. Our Jeans model finds two similarly probable solutions around different dynamical cluster centres. The first solution has a centre close to the photometric estimates available in the literature and does not need an IMBH to fit the observed kinematics. The second solution contains a location of the cluster centre that is offset by about 2.4 arcsec from the first one and it needs an IMBH mass of $4600^{+1700}_{-1400}$ solar masses. N-body models support the existence of an IMBH in this cluster with a mass of up to 6000 solar masses in this cluster, although models without an IMBH provide a better fit to the observed surface brightness profile. They further indicate that the cluster has lost nearly all stellar-mass black holes. We further discuss the detection of two potential high-velocity stars with radial velocities of 80 to 90 km/s relative to the cluster mean., Comment: accepted for publication in MNRAS; data can be found here: https://doi.org/10.25625/VCNHOR
Published: 2021
Full Text: View/download PDF

3. The impact of unresolved magnetic spots on high precision radial velocity measurements

Author: Julien Morin, Pascal Petit, Maksym Lisogorskyi, Ansgar Reiners, Matthew W. Mengel, S. Boro Saikia, Sandra V. Jeffers, Aline A. Vidotto, Hugh R. A. Jones, University of Hertfordshire [Hatfield] (UH), University of Vienna [Vienna], Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), University of Southern Queensland (USQ), Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics, 01 natural sciences, symbols.namesake, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Earth and Planetary Astrophysics (astro-ph.EP), Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, Starspot, Astronomy and Astrophysics, Exoplanet, Magnetic field, Radial velocity, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, symbols, Astrophysics::Earth and Planetary Astrophysics, Doppler effect, Noise (radio), Astrophysics - Earth and Planetary Astrophysics
Abstract: The Doppler method of exoplanet detection has been extremely successful, but suffers from contaminating noise from stellar activity. In this work a model of a rotating star with a magnetic field based on the geometry of the K2 star Epsilon Eridani is presented and used to estimate its effect on simulated radial velocity measurements. A number of different distributions of unresolved magnetic spots were simulated on top of the observed large-scale magnetic maps obtained from eight years of spectropolarimetric observations. The radial velocity signals due to the magnetic spots have amplitudes of up to 10 m s$^{-1}$, high enough to prevent the detection of planets under 20 Earth masses in temperate zones of solar type stars. We show that the radial velocity depends heavily on spot distribution. Our results emphasize that understanding stellar magnetic activity and spot distribution is crucial for detection of Earth analogues., Main text: 7 pages, 3 figures. Appendix: 6 pages, 6 figures. Author name typo corrected. Accepted for publication in MNRAS
Published: 2020
Full Text: View/download PDF

4. Measuring stellar magnetic helicity density

Author: Duncan H. Mackay, Moira Jardine, L. T. Lehmann, Aline A. Vidotto, Colin P. Folsom, Victor See, Sandra V. Jeffers, Stephen C. Marsden, Rim Fares, Julien Morin, K. Lund, J.-F. Donati, Pascal Petit, University of St Andrews [Scotland], University of Exeter, Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), United Arab Emirates University, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Science & Technology Facilities Council, European Research Council, University of St Andrews. School of Physics and Astronomy, and University of St Andrews. Applied Mathematics
Subjects: Stellar mass, FOS: Physical sciences, Astrophysics, 01 natural sciences, Power law, methods: analytical, Magnetic helicity, analytical [Methods], 0103 physical sciences, QB Astronomy, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Sun: magnetic fields, Solar and Stellar Astrophysics (astro-ph.SR), QB, Physics, Magnetic energy, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: magnetic field, DAS, Astronomy and Astrophysics, Helicity, Magnetic field, Solar cycle, magnetic field [Stars], Stars, magnetic fields [Sun], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics
Abstract: Helicity is a fundamental property of a magnetic field but to date it has only been possible to observe its evolution in one star - the Sun. In this paper we provide a simple technique for mapping the large-scale helicity density across the surface of any star using only observable quantities: the poloidal and toroidal magnetic field components (which can be determined from Zeeman-Doppler imaging) and the stellar radius. We use a sample of 51 stars across a mass range of 0.1-1.34 M$_\odot$ to show how the helicity density relates to stellar mass, Rossby number, magnetic energy and age. We find that the large-scale helicity density increases with decreasing Rossby number $R_o$, peaking at $R_o \simeq 0.1$, with a saturation or decrease below that. For both fully- and partially-convective stars we find that the mean absolute helicity density scales with the mean squared toroidal magnetic flux density according to the power law: $|\langle{h\,}\rangle|$ $\propto$ $\langle{\rm{B_{tor}}^2_{}\,\rangle}^{0.86\,\pm\,0.04}$. The scatter in this relation is consistent with the variation across a solar cycle, which we compute using simulations and observations across solar cycles 23 and 24 respectively. We find a significant decrease in helicity density with age., 11 pages, 7 figures
Published: 2020
Full Text: View/download PDF

5. Benchmarking the fundamental parameters of Ap stars with optical long-baseline interferometric measurements

Author: Karine Perraut, Chris Farrington, M. S. Cunha, Nicolas Nardetto, Denis Shulyak, Cyprien Lanthermann, I. Tallon-Bosc, V. Hocdé, T. A. Ryabchikova, Anthony Meilland, Denis Mourard, Frédéric Morand, A. M. Romanovskaya, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institute of Astronomy of the Russian Academy of Sciences (INASAN), Russian Academy of Sciences [Moscow] (RAS), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, Georg-August-University = Georg-August-Universität Göttingen, Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: fundamental parameters [stars], CHEMICALLY PECULIAR STARS, observational [methods], Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, 01 natural sciences, Computer Science::Digital Libraries, Spectral line, Angular diameter, 0103 physical sciences, Astronomical interferometer, Astrophysics::Solar and Stellar Astrophysics, Angular resolution, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, STRATIFICATION ANALYSIS, Science & Technology, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, high angular resolution [techniques], techniques: high angular resolution, Astronomy and Astrophysics, ATMOSPHERE, CATALOG, Exoplanet, Physics::History of Physics, interferometric [techniques], MODEL, Stars, PULSATION, 13. Climate action, Space and Planetary Science, techniques: interferometric, Physical Sciences, ABUNDANCE, stars: fundamental parameters, Astrophysics::Earth and Planetary Astrophysics, EVOLUTIONARY STATUS, methods: observational, Instability strip, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Context. The variety of physical processes at play in chemically peculiar stars makes it difficult to determine their fundamental parameters. In particular, for the magnetic ones, called Ap stars, the strong magnetic fields and the induced spotted stellar surfaces may lead to biased effective temperatures when these values are derived through spectro-photometry. Aims. We propose to benefit from the exquisite angular resolution provided by long-baseline interferometry in the visible to determine the accurate angular diameters of a number of Ap stars, and thus estimate their radii by a method that is as independent as possible of atmospheric models. Methods. We used the visible spectrograph VEGA at the CHARA interferometric array to complete the sample of Ap stars currently observable with this technique. We estimated the angular diameter and radius of six new targets. We estimated their bolometric flux based solely on observational spectroscopic and photometric data to derive nearly model-independent luminosities and effective temperatures. Results. We extend to 14 the number of Ap stars for which interferometric angular diameters have been measured. The fundamental parameters we derived for the complete Ap sample are compared with those obtained through a self-consistent spectroscopic analysis. Based on a model fitting approach of high-resolution spectra and spectro-photometric observations over a wide wavelength range, this method takes into account the anomalous chemical composition of the atmospheres and the inhomogeneous vertical distribution for different chemical elements. Regarding both the radii and the effective temperatures, the derived values from our interferometric observations and from self-consistent modelling are consistent within better than 2σ for nine targets out of ten. We thus benchmark nine Ap stars for effective temperatures ranging from 7200 and 9100 K, and luminosities ranging between 7 L⊙ and 86 L⊙. Conclusions. These results will be key for the future derivation of accurate radii and other fundamental parameters of fainter peculiar stars for which both the sensitivity and the angular resolution of the current interferometers are not sufficient. Within the context of the observations of Ap stars with the Transiting Exoplanet Survey Satellite (TESS), these interferometric measurements are crucial for testing the mechanism of pulsation excitation at work in these peculiar stars. In particular, our interferometric measurements provide accurate locations in the Hertzsprung-Russell diagram for hot Ap stars among which pulsations may be searched for with TESS, putting to test the blue edge of the theoretical instability strip. These accurate locations could be used to derive masses and ages of these stars through a specific grid of models, and to test correlations between the properties of these peculiar stars and their evolutionary state.
Published: 2020
Full Text: View/download PDF

6. A comparison between X-shooter spectra and PHOENIX models across the HR-diagram

Author: Ph. Prugniel, Reynier Peletier, R. Jain, Jesús Falcón-Barroso, Tim-Oliver Husser, Peter H. Hauschildt, Scott Trager, Lucimara Martins, Paula Coelho, Alexandre Vazdekis, P. Sánchez Blázquez, Anais Gonneau, Ariane Lançon, K. Verro, Mariya Lyubenova, A. Arentsen, Yanping Chen, Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leibniz-Institut für Astrophysik Potsdam (AIP), New York University [Abu Dhabi], NYU System (NYU), Departamento de Astronomia, Universidade de São Paulo, Universidade de São Paulo = University of São Paulo (USP), Instituto de Astrofisica de Canarias (IAC), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, European Southern Observatory (ESO), NAT - Universidade Cruzeiro do Sul, ANR-19-CE31-0022,POPSYCLE,Synthèse de populations pour les amas stellaires et les galaxies -atteindre la précision des relevés spectrophotométriques modernes par une physique stellaire renouvelée(2019), European Project: 721463,SUNDIAL, Astronomy, École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Universidade de São Paulo (USP), and Georg-August-University [Göttingen]
Subjects: Stellar population, Hertzsprung–Russell diagram, Continuum (design consultancy), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spectral line, Astronomical spectroscopy, symbols.namesake, Position (vector), stars: atmospheres, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, stars: general, 010303 astronomy & astrophysics, Spectrograph, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: stellar content, symbols, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The path towards robust near-infrared extensions of stellar population models involves the confrontation between empirical and synthetic stellar spectral libraries across the wavelength ranges of photospheric emission. [...] With its near-UV to near-IR coverage, the X-shooter Spectral Library (XSL) allows us to examine to what extent models succeed in reproducing stellar energy distributions (SEDs) and stellar absorption line spectra simultaneously. This study compares the stellar spectra of XSL with the PHOENIX spectra of the G��ttingen Spectral Library. The comparison is carried out both separately in the three arms of the X-shooter spectrograph, and jointly across the whole spectrum. When adopting the stellar parameters published with data release DR2 of XSL, we find that the SEDs of the models are consistent with those of the data at Teff > 5000 K. Below 5000 K, there are significant discrepancies in the SEDs. When leaving the stellar parameters free to adjust, satisfactory representations of the SEDs are obtained down to about 4000 K. However, in particular below 5000 K and in the UVB spectral range, strong local residuals associated with intermediate resolution spectral features are then seen; the necessity of a compromise between reproducing the line spectra and reproducing the SEDs leads to dispersion between the parameters favored by various spectral ranges. We describe the main trends observed and we point out localized offsets between the parameters preferred in this global fit to the SEDs and the parameters in DR2. These depend in a complex way on position in the HR diagram (HRD). We estimate the effect of the offsets on bolometric corrections as a function of position in the HRD and use this for a brief discussion of their impact on the studies of stellar populations. [abridged], Accepted for publication in Astronomy and Astrophysics (24 Nov. 2020). 18 pages (10 figures) in the main text + 19 pages (22 figures) in the appendices (the appendices are spread out for better readability)
Published: 2020
Full Text: View/download PDF

7. Slingshot prominences: coronal structure, mass loss and spin down

Author: See, Victor, Matt, Sean, Finley, Adam, Folsom, Colin, Saikia, Sudeshna Boro, Donati, Jean-François, Fares, Rim, Hebrard, Élodie, Jeffers, Sandra, Marsden, Stephen, Mengel, Matthew, Morin, Julien, Petit, Pascal, Vidotto, Aline, Waite, Ian, Jardine, Moira, Cameron, A Collier, Donati, J-F, Hussain, G, University of St Andrews [Scotland], Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], University of Southern Queensland (USQ), Dublin Institute for Advanced Studies (DIAS), Centre d'Economie de l'Université Paris Nord (ancienne affiliation) (CEPN), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Trinity College Dublin, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, University of St Andrews. St Andrews Centre for Exoplanet Science, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: late-types [Stars], magnetic fields [Stars], FOS: Physical sciences, Astrophysics, coronae [Stars], solar-type [Stars], 01 natural sciences, Solar prominence, stars: rotation, 0103 physical sciences, QB Astronomy, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, QB, Spin-½, stars: coronae, Physics, Slingshot, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, European research, stars: late-type, stars: magnetic field, stars: solar-type, DAS, Astronomy and Astrophysics, rotation [Stars], Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics
Abstract: The structure of a star's coronal magnetic field is a fundamental property that governs the high-energy emission from the hot coronal gas and the loss of mass and angular momentum in the stellar wind. It is, however, extremely difficult to measure. We report a new method to trace this structure in rapidly-rotating young convective stars, using the cool gas trapped on coronal field lines as markers. This gas forms "slingshot prominences" which appear as transient absorption features in H-$\alpha$. By using different methods of extrapolating this field from the surface measurements, we determine locations for prominence support and produce synthetic H-$\alpha$ stacked spectra. The absorption features produced with a potential field extrapolation match well this those observed, while those from a non-potential field do not. In systems where the rotation and magnetic axes are well aligned, up to $50\%$ of the prominence mass may transit the star and so produces a observable feature. This fraction may fall as low as $~2\%$ in very highly inclined systems. Ejected prominences carry away mass and angular momentum at rates that vary by two orders of magnitude, but which may approach those carried by the stellar wind., Comment: 14 pages, 10 figures, accepted by MNRAS
Published: 2019
Full Text: View/download PDF

8. Studying stellar spin-down with Zeeman–Doppler magnetograms

Author: Rim Fares, Colin P. Folsom, Pascal Petit, Victor See, Aline A. Vidotto, Moira Jardine, Stephen C. Marsden, Sandra V. Jeffers, Jean-François Donati, E. Hébrard, S. Boro Saikia, Ian A. Waite, Julien Morin, University of St Andrews [Scotland], Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), York University, University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Bcool, and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Field (physics), FOS: Physical sciences, Flux, Astrophysics, 01 natural sciences, symbols.namesake, stars: rotation, stars: activity, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Spin-½, Physics, Zeeman effect, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, Stellar rotation, Stellar magnetic field, stars: magnetic field, Astronomy, Astronomy and Astrophysics, techniques: polarimetric, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Stellar mass loss, symbols, Astrophysics::Earth and Planetary Astrophysics
Abstract: Magnetic activity and rotation are known to be intimately linked for low-mass stars. Understanding rotation evolution over the stellar lifetime is therefore an important goal within stellar astrophysics. In recent years, there has been increased focus on how the complexity of the stellar magnetic field affects the rate of angular momentum-loss from a star. This is a topic that Zeeman-Doppler imaging (ZDI), a technique that is capable of reconstructing the large-scale magnetic field topology of a star, can uniquely address. Using a potential field source surface model, we estimate the open flux, mass loss-rate and angular momentum-loss rates for a sample of 66 stars that have been mapped with ZDI. We show that the open flux of a star is predominantly determined by the dipolar component of its magnetic field for our choice of source surface radius. We also show that, on the main sequence, the open flux, mass- and angular momentum-loss rates increase with decreasing Rossby number. The exception to this rule is stars less massive than $0.3M_{\odot}$. Previous work suggests that low mass M dwarfs may possess either strong, ordered and dipolar fields or weak and complex fields. This range of field strengths results in a large spread of angular momentum-loss rates for these stars and has important consequences for their spin down behaviour. Additionally, our models do not predict a transition in the mass-loss rates at the so called wind dividing line noted from Ly$\alpha$ studies., Comment: 14 pages, 8 figures, 2 tables, accepted to MNRAS
Published: 2016
Full Text: View/download PDF

9. Do non-dipolar magnetic fields contribute to spin-down torques?

Author: Jean-François Donati, Matthew W. Mengel, Élodie M. Hébrard, Victor See, Aline A. Vidotto, Ian A. Waite, Colin P. Folsom, Pascal Petit, Julien Morin, Stephen C. Marsden, Rim Fares, Sean P. Matt, Sandra V. Jeffers, Moira Jardine, Adam J. Finley, Sudeshna Boro Saikia, University of St Andrews [Scotland], Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, University of Southern Queensland (USQ), Dublin Institute for Advanced Studies (DIAS), Centre d'Economie de l'Université Paris Nord (ancienne affiliation) (CEPN), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Trinity College Dublin, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and Georg-August-University [Göttingen]
Subjects: Angular momentum, 010504 meteorology & atmospheric sciences, Field (physics), FOS: Physical sciences, 01 natural sciences, outflows, stars: low-mass, stars: rotation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Spin-½, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stellar magnetic field, stars: magnetic field, Astronomy and Astrophysics, Function (mathematics), Computational physics, Magnetic field, Dipole, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, magnetohydrodynamics: MHD, [SDU]Sciences of the Universe [physics], stars: winds
Abstract: Main sequence low-mass stars are known to spin-down as a consequence of their magnetised stellar winds. However, estimating the precise rate of this spin-down is an open problem. The mass-loss rate, angular momentum-loss rate and the magnetic field properties of low-mass stars are fundamentally linked making this a challenging task. Of particular interest is the stellar magnetic field geometry. In this work, we consider whether non-dipolar field modes contribute significantly to the spin-down of low-mass stars. We do this using a sample of stars that have all been previously mapped with Zeeman-Doppler imaging. For a given star, as long as its mass-loss rate is below some critical mass-loss rate, only the dipolar fields contribute to its spin-down torque. However, if it has a larger mass-loss rate, higher order modes need to be considered. For each star, we calculate this critical mass-loss rate, which is a simple function of the field geometry. Additionally, we use two methods of estimating mass-loss rates for our sample of stars. In the majority of cases, we find that the estimated mass-loss rates do not exceed the critical mass-loss rate and hence, the dipolar magnetic field alone is sufficient to determine the spin-down torque. However, we find some evidence that, at large Rossby numbers, non-dipolar modes may start to contribute., Comment: 15 pages, 6 figures, 3 tables, accepted to ApJ
Published: 2019
Full Text: View/download PDF

10. NGC6240: A triple nucleus system in the advanced or final state of merging

Author: Ana Monreal-Ibero, Wolfram Kollatschny, Peter M. Weilbacher, M. W. Ochmann, Thierry Contini, Roland Bacon, D. Chelouche, Institut für Astrophysik [Göttingen], and Georg-August-University [Göttingen]
Subjects: Physics, Supermassive black hole, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, Binary number, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Galaxy, Spectral line, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Galaxy formation and evolution, Adaptive optics, 010303 astronomy & astrophysics, Image resolution, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics
Abstract: NGC6240 is a well-studied nearby galaxy system in the process of merging. Based on optical, X-ray, and radio observations, it is thought to harbor two active nuclei We carried out a detailed optical 3D spectroscopic study to investigate the inner region of this system in connection with existing MERLIN and VLBA data. We observed NGC6240 with very high spatial resolution using the MUSE instrument in the Narrow-Field Mode with the four-laser GALACSI adaptive optics system on the ESO VLT under seeing conditions of 0.49 arcsec. Our 3D spectra cover the wavelength range from 4725 to 9350 AA at a spatial resolution of ~75 mas. We report the discovery of three nuclei in the final state of merging within a region of only 1 kpc in the NGC6240 system.Thanks to MUSE we are able to show that the formerly unresolved southern component actually consists of two distinct nuclei separated by only 198 pc. In combination with Gaia data we reach an absolute positional accuracy of only 30 mas that is essential to compare optical spectra with MERLIN and VLBA radio positions. The verification and detailed study of a system with three nuclei, two of which are active and each with a mass in excess of $9\times10^{7} M_{\odot}$, is of great importance for the understanding of hierarchical galaxy formation via merging processes since multiple mergers lead to a faster evolution of massive galaxies in comparison to binary mergers. So far it has been suggested that the formation of galactic nuclei with multiple supermassive black holes (SMBHs) is expected to be rare in the local universe.Triple massive black hole systems might be of fundamental importance for the coalescence of massive black hole binaries in less than a Hubble time leading to the loudest sources of gravitational waves in the millihertz regime., Comment: 15 pages, 13 figures, typos corrected, Astronomy & Astrophysics in press
Published: 2019
Full Text: View/download PDF

11. Galaxy and quasar fueling caught in the act from the intragroup to the interstellar medium

Author: Nicolas Bouché, Raffaella Anna Marino, Sean D. Johnson, Lutz Wisotzki, Edmund Christian Herenz, Hsiao-Wen Chen, Sebastiano Cantalupo, Joop Schaye, Lorrie A. Straka, Michael V. Maseda, John S. Mulchaey, Martin Wendt, Sowgat Muzahid, Wolfram Kollatschny, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Department of Computer Science [ETH Zürich] (D-INFK), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Équipe de droit international, européen et comparé (EDIEC), Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université de Lyon, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Astrophysikalisches Institut Potsdam (AIP), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Leibniz-Institut für Astrophysik Potsdam (AIP), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, Johnson, S, Chen, H, Straka, L, Schaye, J, Cantalupo, S, Wendt, M, Muzahid, S, Bouche, N, Herenz, E, Kollatschny, W, Mulchaey, J, Marino, R, Maseda, M, and Wisotzki, L
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics::High Energy Astrophysical Phenomena, Doubly ionized oxygen, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Luminosity, quasars: general, Galaxy group, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, interactions, intergalactic medium, quasars: individual (PKS 0405–123) [galaxies], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Star formation, Velocity dispersion, Institut für Physik und Astronomie, Astronomy and Astrophysics, Quasar, Astrophysics - Astrophysics of Galaxies, Galaxy, quasars: individual (PKS 0405-123), Interstellar medium, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: interaction, ddc:520
Abstract: We report the discovery of six spatially extended (10-100 kpc) line-emitting nebulae in the z=0.57 galaxy group hosting PKS0405-123, one of the most luminous quasars at z, 9 pages, 3 figures, 2 tables. Accepted to ApJ Letters
Published: 2018
Full Text: View/download PDF

12. Direct evidence of a full dipole flip during the magnetic cycle of a sun-like star

Author: Saikia, S. Boro, Lueftinger, T., Jeffers, S. V, Folsom, C. P., See, V., Petit, P., Marsden, S. C., Vidotto, A. A., Morin, J., Reiners, A., Guedel, M., collaboration, the BCool, University of Vienna [Vienna], Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy [Exeter], University of Exeter, Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Trinity College Dublin, Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Georg-August-University = Georg-August-Universität Göttingen, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Direct evidence, FOS: Physical sciences, Astrophysics, 01 natural sciences, Latitude, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Computer Science::Information Retrieval, Northern Hemisphere, stars: magnetic field, Astronomy and Astrophysics, stars: solar-type, Zeeman–Doppler imaging, stars: imaging, Magnetic field, Dipole, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Middle latitudes, Astrophysics::Earth and Planetary Astrophysics, Dynamo
Abstract: The behaviour of the large-scale dipolar field, during a star's magnetic cycle, can provide valuable insight into the stellar dynamo and associated magnetic field manifestations such as stellar winds. We investigate the temporal evolution of the dipolar field of the K dwarf 61 Cyg A using spectropolarimetric observations covering nearly one magnetic cycle equivalent to two chromospheric activity cycles. The large-scale magnetic field geometry is reconstructed using Zeeman Doppler imaging, a tomographic inversion technique. Additionally, the chromospheric activity is also monitored. The observations provide an unprecedented sampling of the large-scale field over a single magnetic cycle of a star other than the Sun. Our results show that 61 Cyg A has a dominant dipolar geometry except at chromospheric activity maximum. The dipole axis migrates from the southern to the northern hemisphere during the magnetic cycle. It is located at higher latitudes at chromospheric activity cycle minimum and at middle latitudes during cycle maximum. The dipole is strongest at activity cycle minimum and much weaker at activity cycle maximum. The behaviour of the large-scale dipolar field during the magnetic cycle resembles the solar magnetic cycle. Our results are further confirmation that 61 Cyg A indeed has a large-scale magnetic geometry that is comparable to the Sun's, despite being a slightly older and cooler K dwarf., Comment: accepted for publication, A&A Letters
Published: 2018
Full Text: View/download PDF

13. The Rotationally Modulated Polarization of $\xi$ Boo A

Author: Stephen C. Marsden, Pascal Petit, Dag Evensberget, Lucyna Kedziora-Chudczer, Jeremy Bailey, Julien Morin, Sandra V. Jeffers, Daniel V. Cotton, Aline A. Vidotto, B. D. Carter, Kimberly Bott, Jinglin Zhao, Australian Centre for Astrobiology, University of New South Wales [Sydney] (UNSW), University of Southern Queensland (USQ), School of Physics [UNSW Sydney] (UNSW), University of Washington [Seattle], Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Georg-August-University = Georg-August-Universität Göttingen
Subjects: Rotation period, Physics, 010308 nuclear & particles physics, Linear polarization, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stellar rotation, Polarimetry, Astronomy and Astrophysics, Astrophysics, Polarization (waves), 01 natural sciences, Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Hot Jupiter, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics
Abstract: We have observed the active star $\xi$ Boo A (HD 131156A) with high precision broadband linear polarimetry contemporaneously with circular spectropolarimetry. We find both signals are modulated by the 6.43 day rotation period of $\xi$ Boo A. The signals from the two techniques are 0.25 out of phase, consistent with the broadband linear polarization resulting from differential saturation of spectral lines in the global transverse magnetic field. The mean magnitude of the linear polarization signal is ~4 ppm/G but its structure is complex and the amplitude of the variations suppressed relative to the longitudinal magnetic field. The result has important implications for current attempts to detect polarized light from hot Jupiters orbiting active stars in the combined light of the star and planet. In such work stellar activity will manifest as noise, both on the time scale of stellar rotation, and on longer time scales - where changes in activity level will manifest as a baseline shift between observing runs., Comment: 8 pages, 3 figures, 5 tables, published in MNRAS
Published: 2018
Full Text: View/download PDF

14. The CARMENES search for exoplanets around M dwarfs

Author: Kaminski, A., Trifonov, T., Caballero, J. A., Quirrenbach, A., Ribas, I., Reiners, A., Amado, P. J., Zechmeister, M., Dreizler, S., Perger, M., Tal-Or, L., Bonfils, X., Mayor, M., Astudillo-Defru, N., Bauer, F. F., Béjar, V. J. S., Cifuentes, C., Colomé, J., Cortés-Contreras, M., Delfosse, X., Díez-Alonso, E., Forveille, T., Guenther, E. W., Hatzes, A. P., Henning, Th., Jeffers, S. V., Kürster, M., Lafarga, M., Luque, R., Mandel, H., Montes, D., Morales, J. C., Passegger, V. M., Pedraz, S., Reffert, S., Sadegi, S., Schweitzer, A., Seifert, W., Stahl, O., Udry, S., Centre for Research in NanoEngineering, Universitat Politècnica de Catalunya [Barcelona] (UPC), Institut de Ciencies de l'Espai [Barcelona] (ICE-CSIC), Consejo Superior de Investigaciones Científicas [Spain] (CSIC), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Universidad de Concepción [Chile], Thüringer Landessternwarte Tautenburg (TLS), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Universidad de Córdoba [Cordoba], Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Centro Astronómico Hispano Alemán, Observatorio de Calar Alto (CAHA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
Subjects: stars: low-mass, [SDU]Sciences of the Universe [physics], stars: late-type, planetary systems, stars: individual: HD 180617
Abstract: International audience; Despite their activity, low-mass stars are of particular importance for the search of exoplanets by the means of Doppler spectroscopy, as planets with lower masses become detectable. We report on the discovery of a planetary companion around HD 180617, a bright (J = 5.58 mag), low-mass (M = 0.45M⊙) star of spectral type M2.5 V. The star, located at a distance of 5.9 pc, is the primary of the high proper motion binary system containing vB 10, a star with one of the lowest masses known in most of the twentieth century. Our analysis is based on new radial velocity (RV) measurements made at red-optical wavelengths provided by the high-precision spectrograph CARMENES, which was designed to carry out a survey for Earth-like planets around M dwarfs. The available CARMENES data are augmented by archival Doppler measurements from HIRES and HARPS. Altogether, the RVs span more than 16 yr. The modeling of the RV variations, with a semi-amplitude of K = 2.85-0.25+0.16 m s-1, yields a Neptune-like planet with a minimum mass of 12.2-1.4+1.0 M⊕ on a 105.90-0.10+0.09 d circumprimary orbit, which is partly located in the host star's habitable zone. The analysis of time series of common activity indicators does not show any dependence on the detected RV signal. The discovery of HD 180617 b not only adds information to a currently hardly filled region of the mass-period diagram of exoplanets around M dwarfs, but the investigated system becomes the third known binary consisting of M dwarfs and hosting an exoplanet in an S-type configuration. Its proximity makes it an attractive candidate for future studies. The RV data (Table C.1) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A115
Published: 2018
Full Text: View/download PDF

15. Bringing high-spectral resolution to VLT/SPHERE with a fibre coupling to VLT/CRIRES+

Author: Vigan, Arthur, Otten, G. P. P. L., Muslimov, E., Dohlen, K., Phillips, M. W., Seemann, U., Beuzit, J. -L., Dorn, R., Kasper, M., Mouillet, D., Baraffe, I., Reiners, A., Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), School of Physics and Astronomy [Exeter], University of Exeter, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory (ESO), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, and École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL)
Subjects: [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics
Abstract: Atmospheric composition provides essential markers of the most fundamental properties of giant exoplanets, such as their formation mechanism or internal structure. New-generation exoplanet imagers, like VLT/SPHERE or Gemini/GPI, have been designed to achieve very high contrast (>15 mag) at small angular separations ($, Comment: 18 pages, 12 figures. Proceeding of the SPIE Astronomical Telescopes + Instrumentation Conference, 10 - 15 June 2018
Published: 2018

16. Atmospheric Radiation Boundary Conditions for the Helmholtz Equation

Author: Michael Leguèbe, Hélène Barucq, Marc Duruflé, Juliette Chabassier, Laurent Gizon, Advanced 3D Numerical Modeling in Geophysics (Magique 3D), Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Université de Pau et des Pays de l'Adour (UPPA), Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, New York University [Abu Dhabi], NYU System (NYU), ANR-16-MRS3-0019,NumForSun,Méthodes Numériques Avancées pour Ecouter et Explorer le Soleil(2016), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung (MPS), and Georg-August-University [Göttingen]
Subjects: Numerical Analysis, Helmholtz equation, Atmosphere, Applied Mathematics, Mathematical analysis, Rotational symmetry, Spherical coordinate system, Acoustic wave, Radiation boundary condition, [INFO.INFO-NA]Computer Science [cs]/Numerical Analysis [cs.NA], Wave equation, 01 natural sciences, 010101 applied mathematics, Computational Mathematics, Modeling and Simulation, Speed of sound, 0103 physical sciences, Helioseismology, Boundary value problem, 0101 mathematics, 1991 Mathematics Subject Classification. 00A71, 35L05, 85A20, 33C55, 65M60, 010303 astronomy & astrophysics, Analysis, Mathematics
Abstract: International audience; This work offers some contributions to the numerical study of acoustic waves propagating in the Sun and its atmosphere. The main goal is to provide boundary conditions for outgoing waves in the solar atmosphere where it is assumed that the sound speed is constant and the density decays exponentially with radius. Outgoing waves are governed by a Dirichlet-to-Neumann map which is obtained from the factorization of the Helmholtz equation expressed in spherical coordinates. For the purpose of extending the outgoing wave equation to axisymmetric or 3D cases, different approximations are implemented by using the frequency and/or the angle of incidence as parameters of interest. This results in boundary conditions called Atmospheric Radiation Boundary Conditions (ARBC) which are tested in ideal and realistic configurations. These ARBCs deliver accurate results and reduce the computational burden by a factor of two in helioseismology applications.; Ce travail apporte quelques contributions à l'étude numérique des ondes acoustiques se propageant dans le Soleil et son atmosphère. Il se base sur la caractérisa-tion des ondes sortantes dans l'atmosphère représentée par une vitesse constante et une densité décroissant exponentiellement. Les ondes sortantes sont régies par un opérateur Dirichlet-to-Neumann qui est obtenu par la factorisation de l'équation de Helmholtz formulée dans les coordonnées sphériques. Afin d'étendre l'équation des ondes sortantes à des géométries axisymétriques ou 3D, différentes approximations sont menées en util-isant la fréquence et/ou l'angle d'incidence comme paramètres d'intérêt. Ceci mène à des conditions de frontière que nous appelons Conditions de Radiation Atmosphériques (ARBC) et qui sont testées en configuration idéalisées et réalistes. Ces conditions ARBC offrent des résultats précis et réduisent le coût de calcul d'un facteur deux pour le cas du Soleil.
Published: 2018
Full Text: View/download PDF

17. A candidate super-Earth planet orbiting near the snow line of Barnard's star

Author: A. Kaminski, M. Zechmeister, Fabo Feng, Z. M. Berdiñas, Andreas Quirrenbach, J. I. González Hernández, Johanna Teske, Sharon X. Wang, Jose A. Caballero, Yiannis Tsapras, S. V. Jeffers, Mikko Tuomi, Hugh R. A. Jones, M. Lafarga, Artie P. Hatzes, Gavin A. L. Coleman, Julien Morin, D. Montes, E. Rodriguez, Bradford P. Holden, Ansgar Reiners, Edward F. Guinan, Steven S. Vogt, John R. Barnes, A. Suárez Mascareño, M. J. López-González, Ignasi Ribas, Carole A. Haswell, Rafael Rebolo, Guillem Anglada-Escudé, Th. Henning, J. B. P. Strachan, Trifon Trifonov, R. P. Butler, S. Shectman, M. Perger, Man Hoi Lee, Lev Tal-Or, Felipe Murgas, Enrique Herrero, Sabine Reffert, Enric Palle, Stefan Dreizler, Cristina Rodríguez-López, Víctor J. S. Béjar, A. Schweitzer, Walter Seifert, M. Cortés-Contreras, B. Toledo-Padrón, A. Rosich, D. Staab, James S. Jenkins, Pedro J. Amado, Aviv Ofir, Jennifer Burt, Juan Carlos Morales, M. Azzaro, Jeffrey D. Crane, Scott G. Engle, Rachel Street, M. Kürster, Marcin Kiraga, Richard P. Nelson, Institut de Ciencies de l'Espai [Barcelona] (ICE-CSIC), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Instituto Andaluz de Geofísica y Prevención de Desastres Sísmicos [Granada] (IAGPDS), Universidad de Granada (UGR), Universidad de Huelva, Thüringer Landessternwarte Tautenburg (TLS), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Universidad Nacional de Córdoba [Argentina], Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Max Planck Society, Ministerio de Economía y Competitividad (España), European Commission, National Science Foundation (US), Consejo Superior de Investigaciones Científicas (España), Queen Mary University of London, Generalitat de Catalunya, Comisión Nacional de Investigación Científica y Tecnológica (Chile), Swiss National Science Foundation, National Aeronautics and Space Administration (US), and Science and Technology Facilities Council (UK)
Subjects: Astrofísica, Solar System, 010504 meteorology & atmospheric sciences, Red dwarf, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], American Association Of Variable Star Observers (AAVSO), FOS: Physical sciences, Minimum mass, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, Planet, Long-term Modulation, Stellar Rotation Period, 0103 physical sciences, Alpha Centauri, Planet Candidates, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Multidisciplinary, Super-Earth, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy, Astrometry, Radial velocity, Astronomía, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Astrophysics::Earth and Planetary Astrophysics, Zero-point Offsets, Astrophysics - Earth and Planetary Astrophysics
Abstract: Barnard’s star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard’s star is also among the least magnetically active red dwarfs known and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging, astrometry and direct imaging, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard’s star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard’s star, making it an excellent target for direct imaging and astrometric observations in the future. © 2018, Springer Nature Limited., The results are based on observations made with the CARMENES instrument at the 3.5-m telescope of the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain), funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union and the CARMENES Consortium members; the 90-cm telescope at the Sierra Nevada Observatory (Granada, Spain) and the 40-cm robotic telescope at the SPACEOBS observatory (San Pedro de Atacama, Chile), both operated by the Instituto de Astrofisica de Andalucia (IAA); and the 80-cm Joan Oro Telescope (TJO) of the Montsec Astronomical Observatory (OAdM), owned by the Generalitat de Catalunya and operated by the Institute of Space Studies of Catalonia (IEEC). This research was supported by the following institutions, grants and fellowships: Spanish MINECO ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, AYA2016-79425-C3-1-P, AYA2016-79245-C3-2-P, AYA2016-79425-C3-3-P, AYA2015-69350-C3-2-P, ESP2014-54362-P, AYA2014-56359-P, RYC-2013-14875; Generalitat de Catalunya/CERCA programme; Fondo Europeo de Desarrollo Regional (FEDER); German Science Foundation (DFG) Research Unit FOR2544, project JE 701/3-1; STFC Consolidated Grants ST/P000584/1, ST/P000592/1, ST/M001008/1; NSF AST-0307493; Queen Mary University of London Scholarship; Perren foundation grant; CONICYT-FONDECYT 1161218, 3180405; Swiss National Science Foundation (SNSF); Koshland Foundation and McDonald-Leapman grant; and NASA Hubble Fellowship grant HST-HF2-51399.001. J.T. is a Hubble Fellow.
Published: 2018
Full Text: View/download PDF

18. The Solar Wind in Time II: 3D stellar wind structure and radio emission

Author: Colin P. Folsom, Julien Morin, Pascal Petit, D. Ó Fionnagáin, Aline A. Vidotto, Sandra V. Jeffers, Stephen C. Marsden, J. D. do Nascimento, Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Universidade Federal do Rio Grande do Norte [Natal] (UFRN), Harvard-Smithsonian Center for Astrophysics (CfA), and Smithsonian Institution-Harvard University [Cambridge]
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 7. Clean energy, Radio spectrum, Spectral line, Radio telescope, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, Solar mass, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Bremsstrahlung, Astronomy and Astrophysics, Solar wind, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics
Abstract: In this work, we simulate the evolution of the solar wind along its main sequence lifetime and compute its thermal radio emission. To study the evolution of the solar wind, we use a sample of solar mass stars at different ages. All these stars have observationally-reconstructed magnetic maps, which are incorporated in our 3D magnetohydrodynamic simulations of their winds. We show that angular-momentum loss and mass-loss rates decrease steadily on evolutionary timescales, although they can vary in a magnetic cycle timescale. Stellar winds are known to emit radiation in the form of thermal bremsstrahlung in the radio spectrum. To calculate the expected radio fluxes from these winds, we solve the radiative transfer equation numerically from first principles. We compute continuum spectra across the frequency range 100 MHz - 100 GHz and find maximum radio flux densities ranging from 0.05 - 8.3 $\mu$Jy. At a frequency of 1 GHz and a normalised distance of d = 10 pc, the radio flux density follows 0.24 $(\Omega/\Omega_{\odot})^{0.9}$ (d/[10pc])$^2$ $\mu$Jy, where $\Omega$ is the rotation rate. This means that the best candidates for stellar wind observations in the radio regime are faster rotators within distances of 10 pc, such as $\kappa^1$ Ceti (2.83 $\mu$Jy) and $\chi^1$ Ori (8.3 $\mu$Jy). These flux predictions provide a guide to observing solar-type stars across the frequency range 0.1 - 100 GHz in the future using the next generation of radio telescopes, such as ngVLA and SKA., Comment: Accepted to MNRAS, 15 pages, 11 figures
Published: 2018
Full Text: View/download PDF

19. Ionised gas structure of 100 kpc in an over-dense region of the galaxy group COSMOS-Gr30 at z ~ 0.7

Author: David Carton, Leindert Boogaard, Marcella Carollo, Sebastiano Cantalupo, Genevieve Soucail, Stephen Hamer, Peter M. Weilbacher, Thierry Contini, Léo Michel-Dansac, Hayley Finley, R. A. Marino, Johan Richard, Davor Krajnović, Roland Bacon, Benoît Epinat, Adrien Guérou, Wolfram Kollatschny, Jarle Brinchmann, Lutz Wisotzki, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Institut de recherche en astrophysique et planétologie (IRAP), European Southern Observatory (ESO), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Computer Science [ETH Zürich] (D-INFK), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Leibniz-Institut für Astrophysik Potsdam (AIP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden [Leiden], Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Georg-August-University [Göttingen], Epinat, B, Contini, T, Finley, H, Boogaard, L, Guerou, A, Brinchmann, J, Carton, D, Michel-Dansac, L, Bacon, R, Cantalupo, S, Carollo, M, Hamer, S, Kollatschny, W, Krajnovic, D, Marino, R, Richard, J, Soucail, G, Weilbacher, P, and Wisotzki, L
Subjects: Active galactic nucleus, Absorption spectroscopy, astro-ph.GA, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spectral line, Galaxies: kinematics and dynamic, galaxies: groups: general, galaxies: high-redshift, Ionization, Galaxy group, 0103 physical sciences, Tidal force, galaxies: interactions, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, galaxies: kinematics and dynamics, Line (formation), Physics, evolution, intergalactic medium, galaxies: high-redshift [galaxies], 010308 nuclear & particles physics, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Galaxies: interaction, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: evolution
Abstract: We report the discovery of a 10^4 kpc^2 gaseous structure detected in [OII] in an over-dense region of the COSMOS-Gr30 galaxy group at z~0.725 thanks to deep MUSE Guaranteed Time Observations. We estimate the total amount of diffuse ionised gas to be of the order of (~5+-3)x10^10 Msun and explore its physical properties to understand its origin and the source(s) of the ionisation. The MUSE data allow the identification of a dozen of group members embedded in this structure from emission and absorption lines. We extracted spectra from small apertures defined for both the diffuse ionised gas and the galaxies. We investigated the kinematics and ionisation properties of the various galaxies and extended gas regions thanks to line diagnostics (R23, O32 and [OIII]/H\beta) available within the MUSE wavelength range. We compared these diagnostics to photo-ionisation models and shock models. The structure is divided in two kinematically distinct sub-structures. The most extended sub-structure of ionised gas is likely rotating around a massive galaxy and displays filamentary patterns linking some galaxies. The second sub-structure links another massive galaxy hosting an Active Galactic Nucleus to a low mass galaxy but also extends orthogonally to the AGN host disk over ~35 kpc. This extent is likely ionised by the AGN itself. The location of small diffuse regions in the R23 vs. O32 diagram is compatible with photo-ionisation. However, the location of three of these regions in this diagram (low O32, high R23) can also be explained by shocks, which is supported by their large velocity dispersions. One edge-on galaxy shares the same properties and may be a source of shocks. Whatever the hypothesis, the extended gas seems to be non primordial. We favour a scenario where the gas has been extracted from galaxies by tidal forces and AGN triggered by interactions between at least the two sub-structures., Comment: 21 pages, 12 figures, 3 tables, accepted for publication in A&A (27 October 2017)
Published: 2018
Full Text: View/download PDF

20. The energy budget of stellar magnetic fields

Author: Jerome Bouvier, Sandra V. Jeffers, Ian A. Waite, Rim Fares, Lisa Rosén, Pascal Petit, G. A. J. Hussain, Scott G. Gregory, Stephen C. Marsden, Moira Jardine, Victor See, Jean-François Donati, Aline A. Vidotto, J. D. do Nascimento, C. Moutou, Colin P. Folsom, S. Boro Saikia, Julien Morin, SUPA School of Physics and Astronomy [University of St Andrews], University of St Andrews [Scotland]-Scottish Universities Physics Alliance (SUPA), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève = University of Geneva (UNIGE), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, European Southern Observatory (ESO), University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Universidade Federal do Rio Grande do Norte [Natal] (UFRN), Department of Physics and Astronomy [Uppsala], Uppsala University, Université de Genève (UNIGE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Georg-August-University [Göttingen], Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, SUPA School of Physics and Astronomy [St Andrews], University of St Andrews [Scotland], Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), and Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, polarimetric [Techniques], Power law, Techniques - polarimetric, Astronomi, astrofysik och kosmologi, Astronomy, Astrophysics and Cosmology, QB Astronomy, Astrophysics::Solar and Stellar Astrophysics, Stars - magnetic field, QC, Astrophysics::Galaxy Astrophysics, QB, Physics, Toroid, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Stellar rotation, Astronomy, Astronomy and Astrophysics, 3rd-DAS, Zeeman–Doppler imaging, Energy budget, Magnetic field, rotation [Stars], Stars, magnetic field [Stars], QC Physics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Stars - rotation, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], activity [Stars], Dynamo, Stars - activity
Abstract: Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though none are definitive. In this paper, we examine the toroidal fields of a sample of 55 stars with magnetic maps, with masses in the range 0.1-1.5$\,{\rm M}_\odot$. We find that the energy contained in toroidal fields has a power law dependence on the energy contained in poloidal fields. However the power index is not constant across our sample, with stars less and more massive than 0.5$\,{\rm M}_\odot$ having power indices of 0.72$\pm$0.08 and 1.25$\pm$0.06 respectively. There is some evidence that these two power laws correspond to stars in the saturated and unsaturated regimes of the rotation-activity relation. Additionally, our sample shows that strong toroidal fields must be generated axisymmetrically. The latitudes at which these bands appear depend on the stellar rotation period with fast rotators displaying higher latitude bands than slow rotators. The results in this paper present new constraints for future dynamo studies., Comment: 10 pages, 7 figures, 2 tables, submitted to MNRAS (referee's report indicated minor revisions only)
Published: 2015
Full Text: View/download PDF

21. Mapping diffuse interstellar bands in the local ISM on small scales via MUSE 3D spectroscopy

Author: Peter M. Weilbacher, Stefan Dreizler, Philipp Richter, Tim-Oliver Husser, Martin Wendt, Ana Monreal-Ibero, Lutz Wisotzki, Sebastian Kamann, Jarle Brinchmann, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Astrophysikalisches Institut Potsdam (AIP), and Leibniz-Institut für Astrophysik Potsdam (AIP)
Subjects: Physics, Diffuse interstellar band, 010308 nuclear & particles physics, extinction, ISM: structure, Extinction (astronomy), Institut für Physik und Astronomie, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, ISM: lines and bands, Space and Planetary Science, techniques: imaging spectroscopy, Globular cluster, 0103 physical sciences, globular clusters: individual: NGC 6397, Astrophysics::Solar and Stellar Astrophysics, dust, Spectroscopy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Context. We map the interstellar medium (ISM) including the diffuse interstellar bands (DIBs) in absorption toward the globular cluster NGC 6397 using VLT/MUSE. Assuming the absorbers are located at the rim of the Local Bubble we trace structures on the order of mpc (milliparsec, a few thousand AU). Aims. We aimed to demonstrate the feasibility to map variations of DIBs on small scales with MUSE. The sightlines defined by binned stellar spectra are separated by only a few arcseconds and we probe the absorption within a physically connected region. Methods. This analysis utilized the fitting residuals of individual stellar spectra of NGC 6397 member stars and analyzed lines from neutral species and several DIBs in Voronoi-binned composite spectra with high signal-to-noise ratio (S/N). Results. This pilot study demonstrates the power of MUSE for mapping the local ISM on very small scales which provides a new window for ISM observations. We detect small scale variations in Na I and K I as well as in several DIBs within few arcseconds, or mpc with regard to the Local Bubble. We verify the suitability of the MUSE 3D spectrograph for such measurements and gain new insights by probing a single physical absorber with multiple sight lines.
Published: 2017
Full Text: View/download PDF

22. The programme 'accurate masses for SB2 components'

Author: Halbwachs, J.-L., Arenou, F., Boffin, H. M. J., Famaey, B., Jorissen, A., Kiefer, F., Le Bouquin, J.-B., Pourbaix, D., Guillout, P., Ibata, R., Lebreton, Y., Mazeh, T., Nebot Gomez-Moran, A., Tal-Or, L., Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astronomie et d'Astrophysique, Université libre de Bruxelles (ULB), Laboratoire de Génie de la Conception (LGeco), Institut National des Sciences Appliquées - Strasbourg (INSA Strasbourg), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy [Tel Aviv], Tel Aviv University [Tel Aviv], Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Lebreton, Yveline, Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy [Tel Aviv] (TAU), Raymond and Beverly Sackler Faculty of Exact Sciences [Tel Aviv] (TAU), Tel Aviv University (TAU)-Tel Aviv University (TAU), Georg-August-University = Georg-August-Universität Göttingen, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Libre de Bruxelles [Bruxelles] (ULB), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrometry, Astronomie, binaries: visual, [SDU] Sciences of the Universe [physics], Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysique, spectroscopic, binaries: visual, Astrometry [binaries], Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, binaries: spectroscopic
Abstract: Accurate stellar masses are requested in order to improve our understanding of stellar interiors, but they are still rather rare. Fortunately, the forthcoming Gaia Mission will provide astrometric measurements permitting the derivation of the orbital inclinations of nearby binaries which are also observed as double-lined spectroscopic binaries (SB2s) with ground-based telescopes. A programme of radial velocity (RV) measurements was initiated in 2010 with the Sophie spectrograph of the Haute-Provence observatory in order to derive accurate SB2 orbits for a large set of stars. Therefore, combined SB2+astrometric orbits will be derived thanks to Gaia, and masses with errors around 1~\% are expected for both components. The programme includes 70 SB2s, and the accurate SB2 orbits of 24 of them were already derived. In addition, two complementary programmes devoted to southern stars or to late-type dwarf stars were also initiated with the HERMES and the CARMENES spectrographs, respectively. Interferometric measurements were obained with the VLTI/PIONIER for 7 SB2s, and were taken from other sources for 4 others. Currently, combined "visual binary" (VB) +SB2 solutions were derived for 7 binaries, leading to the masses of the components and to the parallaxes. The parallaxes from the Hipparcos 2 catalogue were corrected for orbital motion and compared to our solution, confirming the high quality of Hipparcos 2., Comment: 7 pages, 6 figures, SF2A conference 2017
Published: 2017

23. An Updated 2017 Astrometric Solution for Betelgeuse

Author: Alexander Brown, E. O'Gorman, Pierre Kervella, Leen Decin, Graham M. Harper, A. M. S. Richards, Edward F. Guinan, Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), and Georg-August-University [Göttingen]
Subjects: astro-ph.SR, FOS: Physical sciences, Astrophysics, 01 natural sciences, symbols.namesake, Angular diameter, 0103 physical sciences, 010303 astronomy & astrophysics, Cosmic noise, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Physics, Betelgeuse, [PHYS]Physics [physics], 010308 nuclear & particles physics, Abscissa, Centroid, Astronomy and Astrophysics, Type II supernova, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, symbols, Parallax, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Intensity (heat transfer)
Abstract: We provide an update for the astrometric solution for the Type II supernova progenitor Betelgeuse using the revised Hipparcos Intermediate Astrometric Data (HIAD) of van Leeuwen, combined with existing VLA and new e-MERLIN and ALMA positions. The 2007 Hipparcos refined abscissa measurements required the addition of so-called Cosmic Noise of 2.4 mas to find an acceptable 5-parameter stochastic solution. We find that a measure of radio Cosmic Noise should also be included for the radio positions because surface inhomogeneities exist at a level significant enough to introduce additional intensity centroid uncertainty. Combining the 2007 HIAD with the proper motions based solely on the radio positions leads to a parallax of π =5.27+/- 0.78 mas ({190}-25+33 pc), smaller than the Hipparcos 2007 value of 6.56 ± 0.83 mas ({152}-17+22 pc). Furthermore, combining the VLA and new e-MERLIN and ALMA radio positions with the 2007 HIAD, and including radio Cosmic Noise of 2.4 mas, leads to a nominal parallax solution of 4.51 ± 0.80 mas ({222}-34+48 pc), which, while only 0.7σ different from the 2008 solution of Harper et al., is 2.6σ different from the solution of van Leeuwen. An accurate and precise parallax for Betelgeuse is always going to be difficult to obtain because it is small compared to the stellar angular diameter (θ =44 mas). We outline an observing strategy utilizing future mm and sub-mm high-spatial resolution interferometry that must be used if substantial improvements in the precision and accuracy of the parallax and distance are to be achieved. ispartof: Astrophysical Journal vol:154 issue:1 pages:6- status: published
Published: 2017
Full Text: View/download PDF

24. Kepler observations of the asteroseismic binary HD 176465

Author: Timothy R. Bedding, T. Stahn, H. M. Antia, Yvonne Elsworth, J. P. Marques, Daniel Huber, Amy McQuillan, Michael Bazot, Travis S. Metcalfe, C. Régulo, Guy R. Davies, Jørgen Christensen-Dalsgaard, T. Appourchaux, Timothy R. White, Warrick H. Ball, Savita Mathur, V. Silva Aguirre, Dennis Stello, Rachel Howe, Laurent Gizon, O. L. Creevey, Patrick Gaulme, Rasmus Handberg, Saskia Hekker, Martin Bo Nielsen, Christoffer Karoff, Benoit Mosser, Suzanne Aigrain, Günter Houdek, William J. Chaplin, Tiago L. Campante, Rafael A. García, David Salabert, Othman Benomar, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Kavli Institute for Theoretical Physics [Santa Barbara] (KITP), University of California [Santa Barbara] (UC Santa Barbara), University of California (UC)-University of California (UC), Observatoire de Haute-Provence (OHP), Institut Pythéas (OSU PYTHEAS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), School of Physics [UNSW Sydney] (UNSW), University of New South Wales [Sydney] (UNSW), School of Physics, University of Exeter, Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto = University of Porto, School of Physics and Astronomy, University of Birmingham [Birmingham], Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], Institute for Astronomy [Vienna], University of Vienna [Vienna], National Solar Observatory [Tucson] (NSO/Tucson), National Science Foundation [Arlington] (NSF)-Association of Universities for Research in Astronomy (AURA), Stellar Astrophysics Centre [Aarhus] (SAC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Space Science Institute [Boulder] (SSI), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of California [Santa Barbara] (UCSB), University of California-University of California, Universidade do Porto [Porto], Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Association of Universities for Research in Astronomy (AURA)-National Science Foundation [Arlington] (NSF), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Georg-August-University [Göttingen], Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD), Universidade do Porto, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: Binary number, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asteroseismology, 0103 physical sciences, Binary star, Astrophysics::Solar and Stellar Astrophysics, Stellar structure, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, Oscillation, Spectral density, Astronomy and Astrophysics, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Binary star systems are important for understanding stellar structure and evolution, and are especially useful when oscillations can be detected and analysed with asteroseismology. However, only four systems are known in which solar-like oscillations are detected in both components. Here, we analyse the fifth such system, HD 176465, which was observed by Kepler. We carefully analysed the system's power spectrum to measure individual mode frequencies, adapting our methods where necessary to accommodate the fact that both stars oscillate in a similar frequency range. We also modelled the two stars independently by fitting stellar models to the frequencies and complementary parameters. We are able to cleanly separate the oscillation modes in both systems. The stellar models produce compatible ages and initial compositions for the stars, as is expected from their common and contemporaneous origin. Combining the individual ages, the system is about 3.0$\pm$0.5 Gyr old. The two components of HD 176465 are young physically-similar oscillating solar analogues, the first such system to be found, and provide important constraints for stellar evolution and asteroseismology., Accepted for publication in Astronomy and Astrophysics. 16 pages, 10 figures and 8 tables
Published: 2017
Full Text: View/download PDF

25. A BCool survey of the magnetic fields of planet-hosting solar-type stars

Author: Julien Morin, Aline A. Vidotto, Pascal Petit, Brad D. Carter, Jonathan Horner, Sandra V. Jeffers, Rim Fares, Matthew W. Mengel, Stephen C. Marsden, Rachel King, University of Southern Queensland (USQ), INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Trinity College Dublin, Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Bcool, Georg-August-University = Georg-August-Universität Göttingen, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, symbols.namesake, Planet, 0103 physical sciences, stars: activity, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, planetary systems, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Zeeman effect, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: magnetic field, Astronomy, Astronomy and Astrophysics, line: profiles, Planetary system, Astrophysics - Astrophysics of Galaxies, Magnetic field, Stars, techniques: polarimetric, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), symbols, Astrophysics::Earth and Planetary Astrophysics, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Doppler effect
Abstract: We present a spectropolarimetric snapshot survey of solar-type planet hosting stars. In addition to 14 planet-hosting stars observed as part of the BCool magnetic snapshot survey, we obtained magnetic observations of a further 19 planet-hosting solar-type stars in order to see if the presence of close-in planets had an effect on the measured surface magnetic field (|B$_{\ell}$|). Our results indicate that the magnetic activity of this sample is congruent with that of the overall BCool sample. The effects of the planetary systems on the magnetic activity of the parent star, if any, are too subtle to detect compared to the intrinsic dispersion and correlations with rotation, age and stellar activity proxies in our sample. Four of the 19 newly observed stars, two of which are subgiants, have unambiguously detected magnetic fields and are future targets for Zeeman Doppler Mapping., Comment: 16 pages, 13 figures, Accepted for publication in MNRAS
Published: 2017
Full Text: View/download PDF

26. A BCool magnetic snapshot survey of solar-type stars

Author: J. D. do Nascimento, Brad D. Carter, Michel Aurière, S. Théado, Sandra V. Jeffers, Pascal Petit, A. Morgenthaler, Rim Fares, Jerome Bouvier, Moira Jardine, Ansgar Reiners, Thomas Gastine, J. Lanoux, Julien Morin, Valérie Van Grootel, C. Catala, Jean-François Donati, Renada Konstantinova-Antova, B. Dintrans, François Lignières, Stephen C. Marsden, J. C. Ramirez-Velez, Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), University of St Andrews [Scotland], Universidade Federal do Rio Grande do Norte [Natal] (UFRN), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Bulgarian Academy of Sciences (BAS), Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), Université de Liège, Bcool, Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Georg-August-University [Göttingen], Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Max-Planck-Institut für Sonnensystemforschung (MPS), Universidad Nacional Autónoma de México (UNAM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Future studies, Chromospheric activity, 010504 meteorology & atmospheric sciences, Main-sequence stars, Astrophysics, 01 natural sciences, QB Astronomy, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Magnetic survey, R2C, QC, QB, Physics, ~DC~, Stellar polarimetry, Magnetic field, profiles [Line], Astrophysics - Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, BDC, activity [Stars], FOS: Physical sciences, H-Alpha emission, Astrophysics::Cosmology and Extragalactic Astrophysics, Nearby stars, Active stars, 0103 physical sciences, Galactic disk, Low-mass stars, Disc, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Mean value, Geneva-Copenhagen survey, Astronomy, Stars : magnetic fields, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Zeeman–Doppler imaging, Stars : activity, Stars, Surface differential rotation, QC Physics, 13. Climate action, Space and Planetary Science, Magnetic fields, line : profiles, Main sequence
Abstract: Stellar magnetic field measurements obtained from spectropolarimetry offer key data for activity and dynamo studies, and we present the results of a major high-resolution spectropolarimetric Bcool project magnetic snapshot survey of 170 solar-type stars from observations with the Telescope Bernard Lyot and the Canada-France-Hawaii Telescope. For each target star a high signal-to-noise circularly polarised Stokes V profile has been obtained using Least-Squares Deconvolution, and used to detect surface magnetic fields and measure the corresponding mean surface longitudinal magnetic field ($B_{l}$). Chromospheric activity indicators were also measured. Surface magnetic fields were detected for 67 stars, with 21 of these stars classified as mature solar-type stars, a result that increases by a factor of four the number of mature solar-type stars on which magnetic fields have been observed. In addition, a magnetic field was detected for 3 out of 18 of the subgiant stars surveyed. For the population of K-dwarfs the mean value of $B_{l}$ ($|B_{l}|_{mean}$) was also found to be higher (5.7 G) than $|B_{l}|_{mean}$ measured for the G-dwarfs (3.2 G) and the F-dwarfs (3.3 G). For the sample as a whole $|B_{l}|_{mean}$ increases with rotation rate and decreases with age, and the upper envelope for $|B_{l}|$ correlates well with the observed chromospheric emission. Stars with a chromospheric S-index greater than about 0.2 show a high magnetic field detection rate and so offer optimal targets for future studies. This survey constitutes the most extensive spectropolarimetric survey of cool stars undertaken to date, and suggests that it is feasible to pursue magnetic mapping of a wide range of moderately active solar-type stars to improve understanding of their surface fields and dynamos., 36 pages, 26 figures, 7 tables, submitted to MNRAS
Published: 2014
Full Text: View/download PDF

27. Orbital parameters, chemical composition and magnetic field of the Ap binary HD 98088★

Author: Colin P. Folsom, Evelyne Alecian, Denis Shulyak, K. Likuski, Gregg A. Wade, Oleg Kochukhov, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Royal Military College of Canada, Department of Physics and Astronomy [Uppsala], Uppsala University, Institut für Astrophysik [Göttingen], and Georg-August-University [Göttingen]
Subjects: Magnetism, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Am star, 01 natural sciences, Primary (astronomy), 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, [PHYS]Physics [physics], Orbital elements, Physics, 010308 nuclear & particles physics, Component (thermodynamics), Astronomy, Astronomy and Astrophysics, Magnetic field, Dipole, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: HD 98088 is a synchronised, double-lined spectroscopic binary system with a magnetic Ap primary component and an Am secondary component. We study this rare system using high-resolution MuSiCoS spectropolarimetric data, to gain insight into the effect of binarity on the origin of stellar magnetism and the formation of chemical peculiarities in A-type stars. Using a new collection of 29 high-resolution Stokes VQU spectra we re-derive the orbital and stellar physical parameters and conduct the first disentangling of spectroscopic observations of the system to conduct spectral analysis of the individual stellar components. From this analysis we determine the projected rotational velocities of the stars and conduct a detailed chemical abundance analysis of each component using both the SYNTH3 and ZEEMAN spectrum synthesis codes. The surface abundances of the primary component are typical of a cool Ap star, while those of the secondary component are typical of an Am star. We present the first magnetic analysis of both components using modern data. Using Least-Squares Deconvolution, we extract the longitudinal magnetic field strength of the primary component, which is observed to vary between +1170 and -920 G with a period consistent with the orbital period. There is no field detected in the secondary component. The magnetic field in the primary is predominantly dipolar, with the positive pole oriented approximately towards the secondary., Accepted for publication by MNRAS, 17 pages, 12 figures
Published: 2013
Full Text: View/download PDF

28. Magnetic fields on young, moderately rotating Sun-like stars II. EK Draconis (HD 129333)

Author: Waite, Ian, Marsden, Stephen, Carter, Brad, Pascal Petit, Jeffers, Sandra, Morin, Julien, Vidotto, Aline, Donati, Jean-Francois, the BCool Collaboration, University of Southern Queensland (USQ), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Trinity College Dublin, Bcool, and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, stars: activity, stars: magnetic fields, stars: individual: HD 129333, Differential rotation, Astrophysics::Solar and Stellar Astrophysics, Surface brightness, 010303 astronomy & astrophysics, Chromosphere, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Starspot, Astronomy, Astronomy and Astrophysics, line: profiles, stars: solar-type, Zeeman–Doppler imaging, Magnetic field, Stars, starspots, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Polar, Astrophysics::Earth and Planetary Astrophysics
Abstract: The magnetic fields, activity and dynamos of young solar-type stars can be empirically studied using time-series of spectropolarimetric observations and tomographic imaging techniques such as Doppler imaging and Zeeman Doppler imaging. In this paper we use these techniques to study the young Sun-like star EK Draconis (Sp-Type: G1.5V, HD 129333) using ESPaDOnS at the Canada-France-Hawaii Telescope and NARVAL at the T\`elescope Bernard Lyot. This multi-epoch study runs from late 2006 until early 2012. We measure high levels of chromospheric activity indicating an active, and varying, chromosphere. Surface brightness features were constructed for all available epochs. The 2006/7 and 2008 data show large spot features appearing at intermediate-latitudes. However, the 2012 data indicate a distinctive polar spot. We observe a strong, almost unipolar, azimuthal field during all epochs that is similar to that observed on other Sun-like stars. Using magnetic features, we determined an average equatorial rotational velocity, \Omega_eq, of 2.50 +/- 0.08 rad/d. High levels of surface differential rotation were measured with an average rotational shear, \Delta\Omega, of 0.27 +0.24-0.26 rad/d. During an intensively observed 3-month period from December 2006 until February 2007, the magnetic field went from predominantly toroidal ( approx. 80%) to a more balanced poloidal-toroidal (approx. 40-60%) field. Although the large-scale magnetic field evolved over the epochs of our observations, no polarity reversals were found in our data., Comment: MNRAS: Accepted. 17 pages, 10 figures, 8 tables
Published: 2017
Full Text: View/download PDF

29. Standing on the shoulders of Dwarfs: the $Kepler$ asteroseismic LEGACY sample I - oscillation mode parameters

Author: Anders Bo Justesen, Jørgen Christensen-Dalsgaard, Luca Casagrande, Daniel Huber, Timothy R. White, Victor Silva Aguirre, Jakob Rørsted Mosumgaard, Hans Kjeldsen, Yveline Lebreton, Rasmus Handberg, Warrick H. Ball, Timothy R. Bedding, Sarbani Basu, Guy R. Davies, Mikkel N. Lund, David W. Latham, Günter Houdek, William J. Chaplin, Kuldeep Verma, H. M. Antia, School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], Stellar Astrophysics Centre [Aarhus] (SAC), Aarhus University [Aarhus], Sydney Institute for Astronomy (SIfA), The University of Sydney, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Search for Extraterrestrial Intelligence Institute (SETI), Tata Institute of Fundamental Research [Bombay] (TIFR), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Department of Astronomy [New Haven], Yale University [New Haven], Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Tata Institute for Fundamental Research (TIFR), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Harvard University [Cambridge]-Smithsonian Institution, Georg-August-University = Georg-August-Universität Göttingen, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and Harvard University-Smithsonian Institution
Subjects: oscillations [stars], fundamental parameters [stars], FOS: Physical sciences, Astrophysics, asteroseismology, 01 natural sciences, Asteroseismology, Spectral line, symbols.namesake, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Line (formation), Physics, 010308 nuclear & particles physics, Oscillation, Mode (statistics), Astronomy and Astrophysics, Markov chain Monte Carlo, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, evolution [stars], symbols, Astrophysics::Earth and Planetary Astrophysics
Abstract: The advent of space-based missions like $Kepler$ has revolutionized the study of solar-type stars, particularly through the measurement and modeling of their resonant modes of oscillation. Here we analyze a sample of 66 $Kepler$ main-sequence stars showing solar-like oscillations as part of the $Kepler$ seismic LEGACY project. We use $Kepler$ short-cadence data, of which each star has at least 12 months, to create frequency power spectra optimized for asteroseismology. For each star we identify its modes of oscillation and extract parameters such as frequency, amplitude, and line width using a Bayesian Markov chain Monte Carlo `peak-bagging' approach. We report the extracted mode parameters for all 66 stars, as well as derived quantities such as frequency difference ratios, the large and small separations $\Delta\nu$ and $\delta\nu_{02}$; the behavior of line widths with frequency and line widths at $\nu_{\rm max}$ with $T_{\rm eff}$, for which we derive parametrizations; and behavior of mode visibilities. These average properties can be applied in future peak-bagging exercises to better constrain the parameters of the stellar oscillation spectra. The frequencies and frequency ratios can tightly constrain the fundamental parameters of these solar-type stars, and mode line widths and amplitudes can test models of mode damping and excitation., Comment: 29 pages, 27 Figures, 8 Tables, Accepted for publication in Apj
Published: 2017
Full Text: View/download PDF

30. Efficient scheduling of astronomical observations: Application to the CARMENES radial-velocity survey

Author: Jose A. Caballero, Walter Seifert, M. Perger, Ansgar Reiners, Ignasi Ribas, J. C. Morales, Jaime Guardia, M. Cortés-Contreras, J. Colomé, A. Garcia-Piquer, Andreas Quirrenbach, S. V. Jeffers, Pedro J. Amado, German Research Foundation, Ministerio de Economía y Competitividad (España), European Research Council, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Ciencies de l'Espai [Barcelona] (ICE-CSIC), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], and Georg-August-University = Georg-August-Universität Göttingen
Subjects: Population, Real-time computing, FOS: Physical sciences, Context (language use), Instrumentation: spectrographs, 02 engineering and technology, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Stars: late-type, Surveys, Methods: miscellaneous, 01 natural sciences, Scheduling (computing), law.invention, Telescope, Planet, law, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, miscellaneous [Methods], Instrumentation (computer programming), spectrographs [Instrumentation], education, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Spectrograph, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], education.field_of_study, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Exoplanet, Planetary systems, 13. Climate action, Space and Planetary Science, late-type [Stars], 020201 artificial intelligence & image processing, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Context. Targeted spectroscopic exoplanet surveys face the challenge of maximizing their planet detection rates by means of careful planning. For a large planet survey, the number of possible observation combinations, i.e., the sequence of observations night after night, both in total time and amount of targets, is enormous. Aims. Sophisticated scheduling tools and the improved understanding of the exoplanet population are employed to investigate an efficient and optimal way to plan the execution of observations. This is applied to the CARMENES instrument, which is an optical and infrared high-resolution spectrograph that has started a survey of about 300 M-dwarf stars in search of terrestrial exoplanets. Methods. We used evolutionary computation techniques to create an automatic scheduler that minimizes the idle periods of the telescope and distributes the observations among all the targets using configurable criteria. We simulated the case of the CARMENES survey with a realistic sample of targets, and we estimated the efficiency of the planning tool both in terms of telescope operations and planet detection. Results. Our scheduling simulations produce plans that use about 99% of the available telescope time (including overheads) and optimally distribute the observations among the different targets. Under such conditions, and using current planet statistics, the optimized plan using this tool should allow the CARMENES survey to discover about 65% of the planets with radial-velocity semi-amplitudes greater than 1 ms when considering only photon noise. Conclusions. The simulations using our scheduling tool show that it is possible to optimize the survey planning by minimizing idle instrument periods and fulfilling the science objectives in an efficient manner to maximize the scientific return.© 2017 ESO., We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through grants ESP2013-48391-C4-1-R, ESP2014-57495-C2-2-R, AYA2014-54348-C3-1-R and AYA2014-54348-C3-2-R. A.R. acknowledges support from the European Research Council under the FP7 Starting Grant agreement number 279347 and from DFG grant RE 1664/9-1.
Published: 2017
Full Text: View/download PDF

31. The open flux evolution of a solar-mass star on the main sequence

Author: Colin P. Folsom, Victor See, Julien Morin, S. Boro Saikia, Aline A. Vidotto, Jean-François Donati, Moira Jardine, Rim Fares, Stephen C. Marsden, Sandra V. Jeffers, Pascal Petit, University of St Andrews [Scotland], Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut für Astrophysik [Wien], Universität Wien, INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Bcool, Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: Rotation period, Angular momentum, NDAS, Flux, evolution [Stars], FOS: Physical sciences, Astrophysics, polarimetric [Techniques], 01 natural sciences, Magnetogram, stars: rotation, 0103 physical sciences, stars: activity, QB Astronomy, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, 010303 astronomy & astrophysics, QC, Solar and Stellar Astrophysics (astro-ph.SR), QB, Physics, Solar mass, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stellar rotation, stars: magnetic field, Astronomy and Astrophysics, Magnetic flux, rotation [Stars], Stars, magnetic field [Stars], techniques: polarimetric, QC Physics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, activity [Stars]
Abstract: Magnetic activity is known to be correlated to the rotation period for moderately active main sequence solar-like stars. In turn, the stellar rotation period evolves as a result of magnetised stellar winds that carry away angular momentum. Understanding the interplay between magnetic activity and stellar rotation is therefore a central task for stellar astrophysics. Angular momentum evolution models typically employ spin-down torques that are formulated in terms of the surface magnetic field strength. However, these formulations fail to account for the magnetic field geometry, unlike those that are expressed in terms of the open flux, i.e. the magnetic flux along which stellar winds flow. In this work, we model the angular momentum evolution of main sequence solar-mass stars using a torque law formulated in terms of the open flux. This is done using a potential field source surface model in conjunction with the Zeeman-Doppler magnetograms of a sample of roughly solar-mass stars. We explore how the open flux of these stars varies with stellar rotation and choice of source surface radii. We also explore the effect of field geometry by using two methods of determining the open flux. The first method only accounts for the dipole component while the second accounts for the full set of spherical harmonics available in the Zeeman-Doppler magnetogram. We find only a small difference between the two methods, demonstrating that the open flux, and indeed the spin-down, of main sequence solar-mass stars is likely dominated by the dipolar component of the magnetic field., Comment: 12 pages, 7 figures, accepted to MNRAS
Published: 2017
Full Text: View/download PDF

32. Atmospheric radiation boundary conditions for high frequency waves in time-distance helioseismology

Author: Damien Fournier, Michael Leguèbe, Laurent Gizon, Chris S. Hanson, Marc Duruflé, Hélène Barucq, Juliette Chabassier, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, New York University [Abu Dhabi], NYU System (NYU), Advanced 3D Numerical Modeling in Geophysics (Magique 3D), Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Université de Pau et des Pays de l'Adour (UPPA), Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung (MPS), Georg-August-University [Göttingen], and Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Photosphere, Covariance function, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Atmospheric model, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 01 natural sciences, Seismic wave, Computational physics, 010101 applied mathematics, Spherical geometry, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, Boundary value problem, Helioseismology, Astrophysics::Earth and Planetary Astrophysics, 0101 mathematics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: International audience; The temporal covariance between seismic waves measured at two locations on the solar surface is the fundamental observable in time-distance helioseismology. Above the acoustic cutoff frequency (∼5.3 mHz), waves are not trapped in the solar interior and the covariance function can be used to probe the upper atmosphere. We wish to implement appropriate radiative boundary conditions for computing the propagation of high-frequency waves in the solar atmosphere. We consider the radiative boundary conditions recently developed by Barucq et al. (2017) for atmospheres in which sound-speed is constant and density decreases exponentially with radius. We compute the cross-covariance function using a finite element method in spherical geometry and in the frequency domain. The ratio between first-and second-skip amplitudes in the time-distance diagram is used as a diagnostic to compare boundary conditions and to compare with observations. We find that a boundary condition applied 500 km above the photosphere and derived under the approximation of small angles of incidence accurately reproduces the 'infinite atmosphere' solution for high-frequency waves. When the radiative boundary condition is applied 2 Mm above the photosphere, we find that the choice of atmospheric model affects the time-distance diagram. In particular, the time-distance diagram exhibits double-ridge structure when using a VAL atmospheric model.
Published: 2017
Full Text: View/download PDF

33. The connection between stellar activity cycles and magnetic field topology

Author: G. A. J. Hussain, Moira Jardine, Jean-François Donati, Aline A. Vidotto, Scott G. Gregory, Stephen C. Marsden, Colin P. Folsom, Jerome Bouvier, Rim Fares, Pascal Petit, C. Moutou, Victor See, Sandra V. Jeffers, Julien Morin, Ian A. Waite, S. Boro Saikia, J. D. do Nascimento, University of St Andrews [Scotland], Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), ESO Garching, Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Canada-France-Hawaii Telescope Corporation, Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Universidade Federal do Rio Grande do Norte [Natal] (UFRN), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Bcool, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, Université de Genève = University of Geneva (UNIGE), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Harvard University-Smithsonian Institution, Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), and Smithsonian Institution-Harvard University [Cambridge]
Subjects: 010504 meteorology & atmospheric sciences, Stars - evolution, Polarity (physics), NDAS, FOS: Physical sciences, evolution [Stars], Astrophysics, Stellar classification, Rotation, polarimetric [Techniques], 01 natural sciences, Techniques - polarimetric, stars: rotation, 0103 physical sciences, stars: activity, QB Astronomy, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, Stars - magnetic field, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), QC, 0105 earth and related environmental sciences, QB, Physics, Plane (geometry), [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: magnetic field, Astronomy, Astronomy and Astrophysics, Zeeman–Doppler imaging, Magnetic field, rotation [Stars], T Tauri star, Stars, magnetic field [Stars], techniques: polarimetric, QC Physics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Stars - rotation, BDC, activity [Stars], Stars - activity
Abstract: Zeeman Doppler imaging has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. On the Sun, polarity reversals are a feature of its activity cycle. In this paper, we examine the magnetic properties of stars with existing chromospherically determined cycle periods. Previous authors have suggested that cycle periods lie on multiple branches, either in the cycle period-Rossby number plane or the cycle period-rotation period plane. We find some evidence that stars along the active branch show significant average toroidal fields that exhibit large temporal variations while stars exclusively on the inactive branch remain dominantly poloidal throughout their entire cycle. This lends credence to the idea that different shear layers are in operation along each branch. There is also evidence that the short magnetic polarity switches observed on some stars are characteristic of the inactive branch while the longer chromospherically determined periods are characteristic of the active branch. This may explain the discrepancy between the magnetic and chromospheric cycle periods found on some stars. These results represent a first attempt at linking global magnetic field properties obtained form ZDI and activity cycles., 9 pages, 2 figures, 2 tables, accepted to MNRAS
Published: 2016
Full Text: View/download PDF

34. The solar proxy κ1 Cet and the planetary habitability around the young Sun

Author: D Do Nascimento, J., Vidotto, A. A., Pascal Petit, Folsom, C. P., Porto Mello, G. F., Søren Meibom, Abrevaya, X. C., Ribas, I., Matthieu Castro, Marsden, S., Julien Morin, Jeffers, S. V., Guinan, E., Univ. Federal do Rio G. do Norte, Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Obs. do Valongo, Inst. de Astronom y Fica del Espacio, Institut de Ciències de l'Espai, University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: International audience; Among the solar proxies, κ1 Cet, stands out as potentially having a mass very close to solar and a young age. We report magnetic field measurements and planetary habitability consequences around this star, a proxy of the young Sun when life arose on Earth. Magnetic strength was determined from spectropolarimetric observations and we reconstruct the large-scale surface magnetic field to derive the magnetic environment, stellar winds, and particle flux permeating the interplanetary medium around κ1 Cet. Our results show a closer magnetosphere and mass-loss rate 50 times larger than the current solar wind mass-loss rate when Life arose on Earth, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditions.
Published: 2016

35. A solar-like magnetic cycle on the mature K-dwarf 61 Cyg A (HD 201091)

Author: C. P. Folsom, Jeffrey C. Hall, Robert H. Cameron, Ansgar Reiners, Sandra V. Jeffers, Stephen C. Marsden, Aline A. Vidotto, Julien Morin, Pascal Petit, J.-F. Donati, S. Boro Saikia, V. Perdelwitz, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Lowell Observatory [Flagstaff], Hamburger Sternwarte, Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Trinity College Dublin, Bcool, and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, 010504 meteorology & atmospheric sciences, Field (physics), dynamo / stars: activity / stars: chromospheres / stars: magnetic field / stars: solar-type, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Phase (waves), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Zeeman–Doppler imaging, 01 natural sciences, Magnetic field, Stars, Dipole, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Differential rotation, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Dynamo
Abstract: International audience; The long-term monitoring of magnetic cycles in cool stars is a key diagnostic in understanding how dynamo generation and amplification of magnetic fields occur in stars similar in structure to the Sun. We investigate the temporal evolution of a possible magnetic cycle, determined from its large-scale field, of 61 Cyg A over its activity cycle using spectropolarimetric observations and compare it to the solar case. We use Zeeman Doppler imaging (ZDI) to reconstruct the large-scale magnetic geometry over multiple observational epochs spread over a time span of nine years. We investigate the time evolution of the different components of the large-scale field and compare it with the evolution of its chromospheric activity by measuring the flux in three different chromospheric indicators: Ca II H&K, H-alpha and Ca II infra red triplet lines. We also compare our results with the star's coronal activity using XMM-Newton observations. The large-scale magnetic geometry of 61 Cyg A exhibits polarity reversals in both poloidal and toroidal field components, in phase with the chromospheric activity cycle. We also detect weak solar-like differential rotation with a shear level similar to the Sun. During our observational time span of nine years, 61 Cyg A exhibits solar-like variations in its large-scale field geometry as it evolves from minimum activity to maximum activity and vice versa. During its activity minimum in epoch 2007.59, ZDI reconstructs a simple dipolar geometry which becomes more complex close to activity maximum in epoch 2010.55. The radial field flips polarity and reverts back to a simple geometry in epoch 2013.61. The field is strongly dipolar and the evolution of the dipole component of the field is reminiscent of the solar behaviour. The polarity reversal of the large-scale field indicates a magnetic cycle that is in phase with the chromospheric and coronal cycle.
Published: 2016
Full Text: View/download PDF

36. The magnetic field geometry of cool stars

Author: See, Victor, Jardine, Moira, Vidotto, Aline, Donati, Jean-François, Folsom, Colin, Boro Saikia, Sudeshna, Bouvier, Jerome, Fares, Rim, Gregory, Scott, Hussain, Gaitee, Jeffers, Sandra, Marsden, Stephen, Morin, Julien, Moutou, Claire, do Nascimento, Jose-Dias, Petit, Pascal, Rosen, Lisa, Waite, Ian, Feiden, Gregory A., University of St Andrews [Scotland], Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), SUPA School of Physics and Astronomy [St Andrews], European Southern Observatory (ESO), University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Department of Physics and Astronomy [Uppsala], Uppsala University, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), SUPA School of Physics and Astronomy [University of St Andrews], University of St Andrews [Scotland]-Scottish Universities Physics Alliance (SUPA), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Smithsonian Institution-Harvard University [Cambridge], Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Harvard University-Smithsonian Institution
Subjects: [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stellar magnetic fields, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, spectropolarimetry
Abstract: International audience; Zeeman-Doppler imaging has been used to map the large-scale surface magnetic fields of cool stars across a wide range of stellar masses and rotation periods. The derived field geometries are surprising, with many stars showing strong azimuthal fields that are not observed on the Sun. In this poster, using 100 magnetic maps of over 50 stars, we present results showing how the magnetic field geometry of cool stars varies as a function of fundamental parameters. The stellar mass, and hence internal structure, critically influences the field geometry, although this is modified by the stellar rotation rate. We discuss the implications of these results for dynamo theory and the nature of stellar magnetic activity.
Published: 2016
Full Text: View/download PDF

37. Surface magnetism of cool stars

Author: Heidi Korhonen, Colin P. Folsom, Julien Morin, T. A. Carroll, Rachael M. Roettenbacher, Pascal Petit, John D. Monnier, Oleg Kochukhov, Denis Shulyak, S. V. Jeffers, Rim Fares, Lisa Rosén, Klaus G. Strassmeier, Uppsala University, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Leibniz Institute for Astrophysics Potsdam (AIP), INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], University of Copenhagen = Københavns Universitet (KU), University of Michigan [Ann Arbor], University of Michigan System, Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Surface (mathematics), Topology mapping, Physics, 010504 meteorology & atmospheric sciences, Field (physics), Magnetism, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Magnetic flux, Spectral line, Magnetic field, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract: Magnetic fields are essential ingredients of many physical processes in the interiors and envelopes of cool stars. Yet their direct detection and characterisation is notoriously difficult, requiring high-quality observations and advanced analysis techniques. Significant progress has been recently achieved by several types of direct magnetic field studies on the surfaces of cool active stars. In particular, complementary techniques of the field topology mapping with polarisation data and total magnetic flux measurements from intensity spectra have been systematically applied to different classes of active stars leading to interesting and occasionally controversial results. In this paper we summarise the current status of direct magnetic field studies of cool stars, and investigations of surface inhomogeneities caused by the field, based on the material presented at the Cool Stars 19 splinter session., Summary of the splinter session "Surface Magnetism of Cool Stars" at the Cool Stars 19 conference; to be published in Astronomische Nachrichten
Published: 2016
Full Text: View/download PDF

38. What Can We Learn About Stellar Activity Cycles From ZDI?

Author: See, Victor, Jardine, M., Vidotto, A., Donati, J.-F., Boro saikia, S., Bouvier, J., Fares, R., Folsom, C., Gregory, S., Hussain, G., Jeffers, S., Marsden, S., Morin, J., Moutou, C., Do Nascimento, J. D., Petit, Pascal, Waite, I., University of St Andrews [Scotland], Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), European Southern Observatory (ESO), University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Bcool, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Georg-August-University [Göttingen], Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Harvard University [Cambridge]-Smithsonian Institution, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Feiden, Gregory A, Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), and Smithsonian Institution-Harvard University [Cambridge]
Subjects: cool stars, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stellar magnetic fields, activity cycles, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics
Abstract: International audience; It is known that activity cycles, similar to the 11 year cycle of the Sun, can exist on other stars. Previous work suggests that stars may lie on two branches in a cycle period vs rotation period diagram though there is no definitive explanation for why this should be the case. Fundamentally, activity cycles occur as a result of the underlying dynamo. Indeed, a great deal has been learnt about the Sun's activity cycle by studying how its magnetic field evolves over each activity cycle. In the same way, we should be able to learn about the activity cycles of other stars by studying their magnetic field properties. In this talk, I will present new insights into stellar activity cycles by analysing the magnetic maps of stars that are known to present activity cycles. I will show that stars along each of the branches appear to have different magnetic field topologies.
Published: 2016

39. MUSE crowded field 3D spectroscopy of over 12 000 stars in the globular cluster NGC 6397

Author: Husser, Tim-Oliver, Kamann, Sebastian, Dreizler, Stefan, Wendt, Martin, Wulff, Nina, Bacon, Roland, Wisotzki, Lutz, Brinchmann, Jarle, Weilbacher, Peter, Roth, Martin, Monreal-Ibero, Ana, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Leibniz-Institut für Astrophysik Potsdam (AIP), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Astrophysikalisches Institut Potsdam (AIP), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Universiteit Leiden
Subjects: [PHYS]Physics [physics], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2016
Full Text: View/download PDF

40. Magnetic field and wind of Kappa Ceti: towards the planetary habitability of the young Sun when life arose on Earth

Author: Ignasi Ribas, Stephen C. Marsden, S. Meibom, Pascal Petit, J. D. do Nascimento, G. F. Porto de Mello, Colin P. Folsom, E. F. Guinan, Julien Morin, Sandra V. Jeffers, M. Castro, Aline A. Vidotto, Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Univ. Federal do Rio G. do Norte, Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Obs. do Valongo, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Institut de Ciències de l'Espai, Bcool, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Interplanetary medium, Magnetosphere, Space weather, 01 natural sciences, outflows, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, HIP 15457, Stars - magnetic field, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Planetary habitability, Habitability, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: magnetic field, Astronomy, Astronomy and Astrophysics, stars: individual: HD 20630, Magnetic field, Solar wind, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, stars: winds, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Stars - individual (HD 20630, HIP 15457), Stars - winds, outflows, Astrophysics - Earth and Planetary Astrophysics
Abstract: We report magnetic field measurements for Kappa1~Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic field to derive the magnetic environment, stellar winds and particle flux permeating the interplanetary medium around Kappa1~Cet. Our results show a closer magnetosphere and mass-loss rate of Mdot = 9.7 x 10^{-13} Msol/yr, i.e., a factor 50 times larger than the current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the planet's habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditions, 6 pages, 5 figures, Published at the Astrophysical Journal Letters (ApJL): Manuscript #LET33582
Published: 2016
Full Text: View/download PDF

41. Activity induced variation in spin-orbit angles as derived from Rossiter–McLaughlin measurements

Author: S. Khalafinejad, Amaury H. M. J. Triaud, A. Guzman Mesa, Emmanuel Jehin, Rodrigo F. Díaz, L. M. Serrano, Stéphane Udry, G. Boué, Pedro Figueira, S. Kohl, Nuno C. Santos, Stefan Dreizler, Laetitia Delrez, Mahmoudreza Oshagh, S. Boldt, Elsa Ducrot, João P. Faria, Ansgar Reiners, Artem Burdanov, Michaël Gillon, Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Centre d'Etudes en Reproduction des Carnivores (CERCA), École nationale vétérinaire d'Alfort (ENVA), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Laboratory of Microelectronics USP, Universidade de São Paulo (USP), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Universidade do Porto = University of Porto, Georg-August-University = Georg-August-Universität Göttingen, École nationale vétérinaire - Alfort (ENVA), Universidade de São Paulo = University of São Paulo (USP), and Université de Genève = University of Geneva (UNIGE)
Subjects: spectroscopy, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, Transit (astronomy), Variation (astronomy), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Earth and Planetary Astrophysics (astro-ph.EP), Physics, 010308 nuclear & particles physics, Starspot, Astronomy and Astrophysics, Light curve, Stars, numerical-planetary system-techniques: photometry, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Orbit (dynamics), Astrophysics::Earth and Planetary Astrophysics, methods: observational, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Noise (radio), Astrophysics - Earth and Planetary Astrophysics
Abstract: One of the most powerful methods used to estimate sky-projected spin-orbit angles of exoplanetary systems is through a spectroscopic transit observation known as the Rossiter-McLaughlin (RM) effect. So far mostly single RM observations have been used to estimate the spin-orbit angle, and thus there have been no studies regarding the variation of estimated spin-orbit angle from transit to transit. Stellar activity can alter the shape of photometric transit light curves and in a similar way they can deform the RM signal. In this paper we discuss several RM observations, obtained using the HARPS spectrograph, of known transiting planets that all transit extremely active stars, and by analyzing them individually we assess the variation in the estimated spin-orbit angle. Our results reveal that the estimated spin-orbit angle can vary significantly (up to 42 degrees) from transit to transit, due to variation in the configuration of stellar active regions over different nights. This finding is almost two times larger than the expected variation predicted from simulations. We could not identify any meaningful correlation between the variation of estimated spin-orbit angles and the stellar magnetic activity indicators. We also investigated two possible approaches to mitigate the stellar activity influence on RM observations. The first strategy was based on obtaining several RM observations and folding them to reduce the stellar activity noise. Our results demonstrated that this is a feasible and robust way to overcome this issue. The second approach is based on acquiring simultaneous high-precision short-cadence photometric transit light curves using TRAPPIST/SPECULOOS telescopes, which provide more information about the stellar active region's properties and allow a better RM modeling., 18 pages, 7 figures, 6 tables, accepted for publication in A&A
Published: 2018
Full Text: View/download PDF

42. CFBDS J005910.90-011401.3: reaching the T-Y brown dwarf transition?

Author: Delorme, Philippe, Delfosse, Xavier, Albert, Loic, Artigau, Etienne., Forveille, Thierry, Reylé, Céline, Allard, France, Homeier, Derek, Robin, Annie, Willott, Chris J., Liu, Michael, Dupuy, Trent, Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Gemini Observatory [Southern Operations Center], Association of Universities for Research in Astronomy (AURA), Laboratoire d'astrophysique de l'observatoire de Besançon (LAOB), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Department of Physics [Ottawa], Université d'Ottawa, Institute for Astronomy (IfA), University of Hawai‘i [Mānoa] (UHM), Canada France Brown Dwarf Survey, Institute for Astronomy [Honolulu], Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Physics, University of Ottawa, Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'astrophysique de l'observatoire de Besançon (UMR 6091) (LAOB), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), University of Ottawa [Ottawa], École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Georg-August-University = Georg-August-Universität Göttingen
Subjects: spectroscopy, Proper motion, 010504 meteorology & atmospheric sciences, Brown dwarf, FOS: Physical sciences, Astrophysics, Surveys, Stellar classification, 01 natural sciences, Spectral line, law.invention, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Telescope, Photometry (optics), law, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics (astro-ph), Astronomy and Astrophysics, techniques, spectroscopic, surveys, atmospheres, infrared, stars, low-mass, brown dwarfs, Low mass stars: brown dwarfs, Laser guide star, Thin disk, Space and Planetary Science
Abstract: We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-France-Hawaii Telescope (CFHT), and present optical and near-infrared photometry, Keck laser guide star adaptive optics imaging, and a complete near-infrared spectrum, from 1.0 to 2.2 $\mu$m. A side to side comparison of the near-infrared spectra of CFBDS0059 and ULAS J003402.77-005206.7 (hereafter ULAS0034), previously the coolest known brown dwarf, indicates that CFBDS0059 is ~50+/-15K cooler. We estimate a temperature of Teff ~ 620K and gravity of log g ~ 4.75. Evolutionary models translate these parameters into an age of 1-5 Gyr and a mass of 15-30 M_Jup. We estimate a photometric distance of ~13pc, which puts CFBDS0059 within easy reach of accurate parallax measurements. Its large proper motion suggests membership in the older population of the thin disk. The spectra of both CFBDS0059 and ULAS J0034 shows probable absorption by a wide ammonia band on the blue side of the $H$-band flux peak. If, as we expect, that feature deepens further for still lower effective temperatures, its appearance will become a natural breakpoint for the transition between the T spectral class and the new Y spectral type. CFBDS0059 and ULAS J0034 would then be the first Y0 dwarfs., Comment: 12 pages, Submitted to A&A
Published: 2008
Full Text: View/download PDF

43. A self-consistent dynamo model for fully convective stars

Author: Yadav, Rakesh Kumar, Christensen, Ulrich, Morin, Julien, Gastine, Thomas, Reiners, Ansgar, Katja Poppenhaeger, Wolk, Scott J., Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Queen's University [Belfast] (QUB), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Harvard University [Cambridge]-Smithsonian Institution
Subjects: [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics
Abstract: International audience; The tachocline region inside the Sun, where the rigidly rotating radiative core meets the differentially rotating convection zone, is thought to be crucial for generating the Sun's magnetic field. Low-mass fully convective stars do not possess a tachocline and were originally expected to generate only weak small-scale magnetic fields. Observations, however, have painted a different picture of magnetism in rapidly-rotating fully convective stars: (1) Zeeman broadening measurements revealed average surface field of several kiloGauss (kG), which is similar to the typical field strength found in sunspots. (2) Zeeman-Doppler-Imaging (ZDI) technique discovered large-scale magnetic fields with a morphology often similar to the Earth's dipole-dominated field. (3) Comparison of Zeeman broadening and ZDI results showed that more than 80% of the magnetic flux resides at small scales. So far, theoretical and computer simulation efforts have not been able to reproduce these features simultaneously. Here we present a self-consistent global model of magnetic field generation in low-mass fully convective stars. A distributed dynamo working in the model spontaneously produces a dipole-dominated surface magnetic field of the observed strength. The interaction of this field with the turbulent convection in outer layers shreds it, producing small-scale fields that carry most of the magnetic flux. The ZDI technique applied to synthetic spectropolarimetric data based on our model recovers most of the large-scale field. Our model simultaneously reproduces the morphology and magnitude of the large-scale field as well as the magnitude of the small-scale field observed on low-mass fully convective stars.
Published: 2016

44. Could a change in magnetic field geometry cause the break in the wind-activity relation?

Author: Pascal Petit, Isabelle Boisse, Moira Jardine, Stephen C. Marsden, Jean-François Donati, S. Boro Saikia, E. Hébrard, Julien Morin, Aline A. Vidotto, Victor See, Sandra V. Jeffers, Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève = University of Geneva (UNIGE), Trinity College Dublin, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), SUPA School of Physics and Astronomy [University of St Andrews], University of St Andrews [Scotland]-Scottish Universities Physics Alliance (SUPA), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université de Genève (UNIGE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Georg-August-University [Göttingen], Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Surface (mathematics), Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Outflows, Astrophysics, coronae [Stars], 01 natural sciences, low-mass [Stars], 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, QB Astronomy, winds [Stars], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), QC, QB, Physics, Toroid, Magnetic energy, 010308 nuclear & particles physics, Astronomy and Astrophysics, Function (mathematics), 3rd-DAS, Magnetic field, Stars, QC Physics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Magnetic fields, Jump, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], activity [Stars]
Abstract: Wood et al suggested that mass-loss rate is a function of X-ray flux ($\dot{M} \propto F_x^{1.34}$) for dwarf stars with $F_x \lesssim F_{x,6} \equiv 10^6$ erg cm$^{-2}$ s$^{-1}$. However, more active stars do not obey this relation. These authors suggested that the break at $F_{x,6}$ could be caused by significant changes in magnetic field topology that would inhibit stellar wind generation. Here, we investigate this hypothesis by analysing the stars in Wood et al's sample that had their surface magnetic fields reconstructed through Zeeman-Doppler Imaging (ZDI). Although the solar-like outliers in the $\dot{M}$ -- $F_x$ relation have higher fractional toroidal magnetic energy, we do not find evidence of a sharp transition in magnetic topology at $F_{x,6}$. To confirm this, further wind measurements and ZDI observations at both sides of the break are required. As active stars can jump between states with highly toroidal to highly poloidal fields, we expect significant scatter in magnetic field topology to exist for stars with $F_x \gtrsim F_{x,6}$. This strengthens the importance of multi-epoch ZDI observations. Finally, we show that there is a correlation between $F_x$ and magnetic energy, which implies that $\dot{M}$ -- magnetic energy relation has the same qualitative behaviour as the original $\dot{M}$ -- $F_x$ relation. No break is seen in any of the $F_x$ -- magnetic energy, Comment: 7 pages, 3 figures, 4 tables, accepted to MNRAS Letters
Published: 2016
Full Text: View/download PDF

45. Masses of the components of SB2 binaries observed with Gaia. III. Accurate SB2 orbits for 10 binaries and masses of HIP 87895

Author: Frédéric Arenou, Patrick Guillout, A. Nebot Gomez-Moran, Tsevi Mazeh, Caroline Soubiran, J.-B. Salomon, Yveline Lebreton, Jean-Louis Halbwachs, Dimitri Pourbaix, Lev Tal-Or, Benoit Famaey, Flavien Kiefer, Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université libre de Bruxelles (ULB), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), M2A 2016, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and Georg-August-University = Georg-August-Universität Göttingen
Subjects: FOS: Physical sciences, Binary number, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Spectral line, Observatory, Primary (astronomy), stars: individual:HIP 87895, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Spectrograph, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Orbital elements, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Methods observational, Large sample, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, stars: fundamental parameters, binaries: spectroscopic
Abstract: In anticipation of the Gaia astrometric mission, a large sample of spectroscopic binaries has been observed since 2010 with the SOPHIE spectrograph at the Haute--Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1 % when the astrometric measurements of Gaia are taken into account. In this paper we present the results from five years of observations of 10 SB2 systems with periods ranging from 37 to 881 days. Using the TODMOR algorithm we computed radial velocities from the spectra, and then derived the orbital elements of these binary systems. The minimum masses of the components are then obtained with an accuracy better than 1.2 % for the ten binaries. Combining the radial velocities with existing interferometric measurements, we derived the masses of the primary and secondary components of HIP 87895 with an accuracy of 0.98 % and 1.2 % respectively., Comment: 9 pages, 3 figures, 6 tables, Monthly Notices of the Royal Astronomical Society (2016)
Published: 2016
Full Text: View/download PDF

46. The evolution of surface magnetic fields in young solar-type stars I: the first 250 Myr

Author: Colin P. Folsom, Agnès Lèbre, Aline A. Vidotto, Ana Palacios, Louis Amard, Stephen C. Marsden, Sandra V. Jeffers, Pascal Petit, Julien Morin, Jerome Bouvier, Jean-François Donati, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Genève (UNIGE), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Computational Engineering and Science Research Centre, University of Southern Queensland (USQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: FOS: Physical sciences, Astrophysics, Rotation, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy, Astronomy and Astrophysics, Observable, equipment and supplies, Zeeman–Doppler imaging, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Magnetic field, T Tauri star, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, human activities, Dynamo, Open cluster
Abstract: The surface rotation rates of young solar-type stars vary rapidly with age from the end of the pre-main sequence through the early main sequence. Important changes in the dynamos operating in these stars may result from this evolution, which should be observable in their surface magnetic fields. Here we present a study aimed at observing the evolution of these magnetic fields through this critical time period. We observed stars in open clusters and stellar associations of known ages, and used Zeeman Doppler Imaging to characterize their complex magnetic large-scale fields. Presented here are results for 15 stars, from 5 associations, with ages from 20 to 250 Myr, masses from 0.7 to 1.2 solar masses, and rotation periods from 0.4 to 6 days. We find complex large-scale magnetic field geometries, with global average strengths from 14 to 140 G. There is a clear trend towards decreasing average large-scale magnetic field strength with age, and a tight correlation between magnetic field strength and Rossby number. Comparing the magnetic properties of our zero-age main sequence sample to those of both younger and older stars, it appears that the magnetic evolution of solar-type stars during the pre-main sequence is primarily driven by structural changes, while it closely follows the stars' rotational evolution on the main sequence., 31 pages, accepted for publication in MNRAS
Published: 2016
Full Text: View/download PDF

47. The UK Met Office global circulation model with a sophisticated radiation scheme applied to the hot Jupiter HD 209458b

Author: James Manners, David M. Acreman, Chris Smith, Derek Homeier, Nathan J. Mayne, Isabelle Baraffe, Benjamin Drummond, Pascal Tremblin, David S. Amundsen, University of Exeter, Department of Applied Physics and Applied Mathematics [New York], Columbia University [New York], NASA Goddard Institute for Space Studies (GISS), NASA Goddard Space Flight Center (GSFC), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), United Kingdom Met Office [Exeter], Maison de la Simulation (MDLS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg] = Heidelberg University, European Project: 247060,EC:FP7:ERC,ERC-2009-AdG,PEPS(2010), European Project: 320478,EC:FP7:ERC,ERC-2012-ADG_20120216,TOFU(2013), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Nordregio, Institut für Astrophysik [Göttingen], and Georg-August-University [Göttingen]
Subjects: Offset (computer science), 010504 meteorology & atmospheric sciences, Opacity, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics, 01 natural sciences, methods: numerical, Atmosphere, 0103 physical sciences, Hot Jupiter, Radiative transfer, Emission spectrum, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Physics, planets and satellites: atmospheres, Astronomy and Astrophysics, Unified Model, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Exoplanet, planets and satellites: gaseous planets, 13. Climate action, Space and Planetary Science, radiative transfer, hydrodynamics, Astrophysics::Earth and Planetary Astrophysics
Abstract: International audience; To study the complexity of hot Jupiter atmospheres revealed by observations of increasing quality, we have adapted the UK Met Office Global Circulation Model (GCM), the Unified Model (UM), to these exoplanets. The UM solves the full 3D Navier-Stokes equations with a height-varying gravity, avoiding the simplifications used in most GCMs currently applied to exoplanets. In this work we present the coupling of the UM dynamical core to an accurate radiation scheme based on the two-stream approximation and correlated-k method with state-of-the-art opacities from ExoMol. Our first application of this model is devoted to the extensively studied hot Jupiter HD 209458b. We have derived synthetic emission spectra and phase curves, and compare them to both previous models also based on state-of-the-art radiative transfer, and to observations. We find a reasonable agreement between observations and both our days side emission and hot spot offset, however, our night side emissions is too large. Overall our results are qualitatively similar to those found by Showman et al. (2009, ApJ, 699, 564) with the SPARC/MITgcm, however, we note several quantitative differences: Our simulations show significant variation in the position of the hottest part of the atmosphere with pressure, as expected from simple timescale arguments, and in contrast to the “vertical coherency” found by Showman et al. (2009). We also see significant quantitative differences in calculated synthetic observations. Our comparisons strengthen the need for detailed intercomparisons of dynamical cores, radiation schemes and post-processing tools to understand these differences. This effort is necessary in order to make robust conclusions about these atmospheres based on GCM results.
Published: 2016
Full Text: View/download PDF

48. A terrestrial planet candidate in a temperate orbit around Proxima Centauri

Author: Michael Endl, Mikko Tuomi, Pedro J. Amado, John R. Barnes, Martin Kürster, Aviv Ofir, Marcin Kiraga, Jose Luis Ortiz, Sandra V. Jeffers, Stefan Dreizler, L. F. Sarmiento, Guillem Anglada-Escudé, Julien Morin, R. Paul Butler, E. Rodriguez, J. B. P. Strachan, Richard P. Nelson, James S. Jenkins, Cristina Rodrίguez-López, Ignacio de la Cueva, Nicolás Morales, Marίa J. López-González, Benjamin Giesers, Z. M. Berdiñas, Mathias Zechmeister, Hugh R. A. Jones, Ansgar Reiners, Yiannis Tsapras, Sijme-Jan Paardekooper, Christopher Marvin, Gavin A. L. Coleman, Ministerio de Economía y Competitividad (España), Junta de Andalucía, Fondo Nacional de Desarrollo Científico y Tecnológico (Chile), Science and Technology Facilities Council (UK), European Research Council, German Research Foundation, National Science Foundation (US), Queen Mary University of London (QMUL), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), The Open University [Milton Keynes] (OU), Department of Terrestrial Magnetism [Carnegie Institution], Carnegie Institution for Science [Washington], Astroimagen, Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], McDonald Observatory, University of Texas at Austin [Austin], Universidad de Chile = University of Chile [Santiago] (UCHILE), University of Hertfordshire [Hatfield] (UH), University of Warsaw (UW), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Weizmann Institute of Science [Rehovot, Israël], Astronomisches Rechen-Institut, and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Rotation period, Extraterrestrial Environment, Rotation, 010504 meteorology & atmospheric sciences, Red dwarf, Astrophysics::High Energy Astrophysical Phenomena, Astronomical unit, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Planets, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Luminosity, Stars, Celestial, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 10. No inequality, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Solar mass, Multidisciplinary, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Temperature, Water, Astronomy, Effective temperature, 13. Climate action, Terrestrial planet, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Anglada-Escude, Guillem et. al., At a distance of 1.295 parsecs(1), the red dwarf Proxima Centauri (a Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun's closest stellar neighbour and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun2 and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity(4) are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface(5)., The authors acknowledge support from the following funding grants: Leverhulme Trust/UK RPG-2014-281 (H. R. A. J., G. A.-E. and M. T.); MINECO/Spain AYA-2014-54348-C3-1-R (P. J. A., C. R.-L., Z. M. B. and E. R.); MINECO/Spain ESP2014-54362-P (M. J. L.-G.); MINECO/Spain AYA-2014-56637-C2-1-P (J. L. O. and N. M.); J. A./Spain 2012-FQM1776 (J. L. O. and N. M.); CATA-Basal/Chile PB06 Conicyt (J. S. J.); Fondecyt/Chile project # 1161218 (J. S. J.); STFC/UK ST/M001008/1 (R. P. N., G. A. L. C. and G. A.-E.); STFC/UK ST/L000776/1 (J. B.); ERC/EU Starting Grant # 279347 (A. R., L. F. S. and S. V. J.); DFG/Germany Research Grants RE 1664/9-2 (A. R.); RE 1664/12-1 (M. Z.); DFG/Germany Colloborative Research Center 963 (C. J. M. and S. D.); DFG/Germany Research Training Group 1351 (L. F. S.); and NSF/USA grant AST-1313075 (M. E.).
Published: 2016
Full Text: View/download PDF

49. Long-term evolution of the large-scale magnetic fields of cool stars

Author: Vidotto, A. a., Gregory, S. G., Jardine, M., Donati, J. -F., Petit, P., MORIN, Julien, Folsom, C. P., Bouvier, J., Cameron, A. C., Hussain, G., Marsden, S., Waite, I. a., Fares, R., Jeffers, S. V., Do Nascimento, J.D. Jr, Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), University of St Andrews [Scotland], University of St Andrews, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), ESO Garching, University of Southern Queensland (USQ), INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Universidade Federal do Rio Grande do Norte [Natal] (UFRN), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We investigate how the large-scale surface magnetic fields of cool dwarf stars, reconstructed using the Zeeman-Doppler Imaging (ZDI) technique, vary with age, rotation period, Rossby number and X-ray emission. Our sample consists of 104 magnetic maps of 76 stars, from accreting pre-main sequence to main-sequence objects, spanning ages from ~1 Myr to ~10 Gyr. For non-accreting dwarfs we empirically find that the unsigned average large-scale surface magnetic field relates to age as age-0.65. This relation has a similar power dependency to that identified in the seminal work of Skumanich (1972). We also find in our data evidence for a linear-type dynamo, in which the surface field is linearly dependent on the rotation rate. The trends we find for large-scale stellar magnetism from ZDI studies are consistent with the trends found from Zeeman broadening measurements, which are sensitive to the unsigned large- and small-scale magnetic field. These similarities indicate that the fields recovered from both techniques are coupled to each other, suggesting that small- and large-scale fields could share the same dynamo field generation processes. Our results are relevant for investigations of rotational evolution of low-mass stars and give important observational constraints for stellar dynamo studies.
Published: 2015

50. Solving the forward problem of helioseismology in the frequency domain

Author: Gizon, Laurent, Barucq, Hélène, Duruflé, Marc, Birch, C. Aaron, Chabassier, Juliette, Fournier, Damien, Hanson, Cristopher, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut für Astrophysik [Göttingen], Georg-August-University = Georg-August-Universität Göttingen, Advanced 3D Numerical Modeling in Geophysics (Magique 3D), Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS), Institut für Numerische und Angewandte Mathematik [Göttingen] (NAM), Max-Planck-Institut für Sonnensystemforschung (MPS), Georg-August-University [Göttingen], and Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, [INFO.INFO-NA]Computer Science [cs]/Numerical Analysis [cs.NA]
Abstract: International audience; Solar acoustic waves are continuously excited by turbulent convection (a random process). The forward problem of local helioseismology was specified at the Waves 2013 conference: computing the cross-covariance of the wave field between any two locations on the solar surface. Here we solve the problem in the frequency domain using the finite element solver Montjoie. One of the specificities of propagation/scattering problems in the Sun is the very sharp decrease of sound speed and density with radius near the surface. We show that the problem simplifies considerably under the assumption that the co-variance function of the source of excitation is proportional to the attenuation.
Published: 2015

Catalog

Books, media, physical & digital resources

See catalog results

Searchworks

Select search scope, currently: Articles Catalog books, media & more in Jio Institute collections Articles journal articles & other e-resources

Search

Search Constraints

Refine your results

Search Limiters

Topic

Publication Year Range

Language

Publication Type

Journal

Database

Publisher

90 results on '"Institut für Astrophysik [Göttingen]"'

Search Results

Catalog

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources