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1. Oscillations of Fluid Tori around Neutron Stars

Author: Eva Šrámková, Monika Matuszková, Kateřina Klimovičová, Jiři Horák, Odele Straub, Gabriela Urbancová, Martin Urbanec, Vladimír Karas, Gabriel Török, and Debora Lančová
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract: We examine the influence of quadrupole moment of a slowly rotating neutron star (NS) on the oscillations of a fluid accretion disk (torus) orbiting a compact object the spacetime around which is described by the Hartle-Thorne geometry. Explicit formulae for non-geodesic orbital epicyclic and precession frequencies, as well as their simplified practical versions that allow for an expeditious application of the universal relations determining the NS properties, are obtained and examined. We demonstrate that the difference in the accretion disk precession frequencies for NSs of the same mass and angular momentum, but different oblateness, can reach up to tens of percent. Even higher differences can arise when NSs with the same mass and rotational frequency, but different equations of state (EoS), are considered. In particular, the Lense-Thirring precession frequency defined in the innermost parts of the accretion region can differ by more than one order of magnitude across NSs with different EoS. Our results have clear implications for models of the LMXBs variability., Comment: Proceeding of IWARA 2022 (Astronomische Nachrichten), 4 pages, 2 figures
Published: 2023
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2. Spectra of Puffy Accretion Discs: the kynbb Fit

Author: Debora Lančová, Anastasiya Yilmaz, Maciek Wielgus, Michal Dovčiak, Odele Straub, and Gabriel Török
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Puffy disc is a numerical model, expected to capture the properties of the accretion flow in X-ray black hole binaries in the luminous, mildly sub-Eddington state. We fit the kerrbb and kynbb spectral models in XSPEC to synthetic spectra of puffy accretion discs, obtained in general relativistic radiative magnetohydrodynamic simulations, to see if they correctly recover the black hole spin and mass accretion rate assumed in the numerical simulation. We conclude that neither of the two models is capable of correctly interpreting the puffy disc parameters, which highlights a necessity to develop new, more accurate, spectral models for the luminous regime of accretion in X-ray black hole binaries. We propose that such spectral models should be based on the results of numerical simulations of accretion., Comment: 6 pages, 4 figures, submitted to the AN as proceedings of XMM-Newton 2022 Science Workshop
Published: 2022
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3. Flaremodel: an open-source Python package for one-zone numerical modelling of synchrotron sources

Author: Odele Straub, P. T. de Zeeuw, Maryam Habibi, A. Drescher, S. von Fellenberg, Julia Stadler, M. Bauboeck, Gabriele Ponti, A. Young, G. Witzel, R. Genzel, T. Ott, Frank Eisenhauer, S. Gillesen, Felix Widmann, and Y. Dallilar
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Stars: Black Holes, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Python (programming language), Synchrotron, law.invention, Open source, Space and Planetary Science, law, Radiation Mechanisms: Non-Thermal, Computer graphics (images), Radiative Transfer, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), computer, computer.programming_language
Abstract: Synchrotron processes, the radiative processes associated with the interaction of energetic charged particles with magnetic field, are of interest in many areas in astronomy, from the interstellar medium to extreme environments near compact objects. Consequently, observations of synchrotron sources carry information on the physical properties of the sources themselves and those of their close vicinity. In recent years, novel observations of such sources with multi-wavelength collaborations reveal complex features and peculiarities, especially near black holes. Exploring the nature of these sources in more detail necessitates numerical tools complementary to analytical one-zone modelling efforts. In this paper, we introduce an open-source Python package tailored to this purpose, FLAREMODEL. The core of the code consists of low-level utility functions to describe physical processes relevant to synchrotron sources, which are written in C for performance and parallelised with OpenMP for scalability. The Python interface provides access to these functions and built-in source models are provided as a guidance. At the same time, the modular design of the code and the generic nature of these functions enable users to build a variety of source models applicable to many astrophysical synchrotron sources. We describe our methodology and the structure of our code along with selected examples demonstrating capabilities and options for future modelling efforts.
Published: 2022

4. Observational properties of puffy disks: radiative GRMHD spectra of mildly sub-Eddington accretion

Author: Maciek Wielgus, Debora Lančová, Odele Straub, Włodek Kluźniak, Ramesh Narayan, David Abarca, Agata Różańska, Frederic Vincent, Gabriel Török, and Marek Abramowicz
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology, Astrophysics::Galaxy Astrophysics
Abstract: Numerical general relativistic radiative magnetohydrodynamic simulations of accretion discs around a stellar-mass black hole with a luminosity above 0.5 of the Eddington value reveal their stratified, elevated vertical structure. We refer to these thermally stable numerical solutions as puffy discs. Above a dense and geometrically thin core of dimensionless thickness h/r ∼ 0.1, crudely resembling a classic thin accretion disc, a puffed-up, geometrically thick layer of lower density is formed. This puffy layer corresponds to h/r ∼ 1.0, with a very limited dependence of the dimensionless thickness on the mass accretion rate. We discuss the observational properties of puffy discs, particularly the geometrical obscuration of the inner disc by the elevated puffy region at higher observing inclinations, and collimation of the radiation along the accretion disc spin axis, which may explain the apparent super-Eddington luminosity of some X-ray objects. We also present synthetic spectra of puffy discs, and show that they are qualitatively similar to those of a Comptonized thin disc. We demonstrate that the existing xspec spectral fitting models provide good fits to synthetic observations of puffy discs, but cannot correctly recover the input black hole spin. The puffy region remains optically thick to scattering; in its spectral properties, the puffy disc roughly resembles that of a warm corona sandwiching the disc core. We suggest that puffy discs may correspond to X-ray binary systems of luminosities above 0.3 of the Eddington luminosity in the intermediate spectral states.
Published: 2022
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5. A geometric distance to the supermassive black Hole of NGC 3783

Author: N. M. Förster Schreiber, M. L. Bolzer, Pierre-Olivier Petrucci, E. Sturm, Jason Dexter, Thibaut Paumard, Florentin Millour, Christopher A. Onken, Christian Straubmeier, Sebastian F. Hönig, Daniel Rouan, Makoto Kishimoto, Reinhard Genzel, Yann Clénet, P. T. de Zeeuw, Julien Woillez, Ric Davies, D. Kaltenbrunner, António Amorim, A. Drescher, Jinyi Shangguan, S. von Fellenberg, D. Gratadour, Misty C. Bentz, Linda J. Tacconi, J. Stadler, Karine Perraut, Felix Widmann, P. Vermot, Amiel Sternberg, Thomas Ott, Paulo J. V. Garcia, Rachel Street, Wolfgang Brandner, Odele Straub, Dieter Lutz, Hagai Netzer, Mercedes Prieto, Taro Shimizu, Stefan Gillessen, Konrad R. W. Tristram, Oliver Pfuhl, M. Bauböck, Frank Eisenhauer, Andreas Eckart, Guy Perrin, Sylvestre Lacour, 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 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), 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]), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), 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), and GRAVITY
Subjects: Length scale, Gravity (chemistry), Cosmology and Nongalactic Astrophysics (astro-ph.CO), Galaxies: Seyfert, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, symbols.namesake, Angular diameter, 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Galaxies: nuclei, Physics, Supermassive black hole, Distance scale, Quasars: individual: NGC 3783, Astronomy and Astrophysics, Galaxies: active, Light curve, Astrophysics - Astrophysics of Galaxies, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), symbols, Reverberation mapping, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Hubble's law, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The angular size of the broad line region (BLR) of the nearby active galactic nucleus (AGN) NGC 3783 has been spatially resolved by recent observations with VLTI/GRAVITY. A reverberation mapping (RM) campaign has also recently obtained high quality light curves and measured the linear size of the BLR in a way that is complementary to the GRAVITY measurement. The size and kinematics of the BLR can be better constrained by a joint analysis that combines both GRAVITY and RM data. This, in turn, allows us to obtain the mass of the supermassive black hole in NGC3783 with an accuracy that is about a factor of two better than that inferred from GRAVITY data alone. We derive $M_\mathrm{BH}=2.54_{-0.72}^{+0.90}\times 10^7\,M_\odot$. Finally, and perhaps most notably, we are able to measure a geometric distance to NGC 3783 of $39.9^{+14.5}_{-11.9}$ Mpc. We are able to test the robustness of the BLR-based geometric distance with measurements based on the Tully-Fisher relation and other indirect methods. We find the geometric distance is consistent with other methods within their scatter. We explore the potential of BLR-based geometric distances to directly constrain the Hubble constant, $H_0$, and identify differential phase uncertainties as the current dominant limitation to the $H_0$ measurement precision for individual sources., 9 pages and 5 figures in main text, Accepted for publication in A&A
Published: 2021
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6. Constraining particle acceleration in Sgr A⋆ with simultaneous GRAVITY, Spitzer, NuSTAR, and Chandra observations

Author: Wolfgang Brandner, A. Jiménez-Rosales, Mark Gurwell, Stefan Hippler, Christian Straubmeier, Th. Henning, Fiona A. Harrison, Jason Dexter, N. M. Förster Schreiber, F. Vincent, Pierre Kervella, Daryl Haggard, S. Yazici, Silvia Scheithauer, Oliver Pfuhl, Y. Dallilar, T. Taro Shimizu, Idel Waisberg, Odele Straub, K. Foster, Felix Widmann, Sera Markoff, Dieter Lutz, J.-B. Le Bouquin, M. Bauböck, Matthew Horrobin, Yann Clénet, P. T. de Zeeuw, Gabriele Ghisellini, Howard A. Smith, Frederick K. Baganoff, Daniel Stern, Thibaut Paumard, Eckhard Sturm, Ric Davies, M. Nowak, Andreas Eckart, Andreas Kaufer, Sebastian Rabien, Laurent Jocou, Paulo J. V. Garcia, Ekkehard Wieprecht, Reinhard Genzel, Jinyi Shangguan, G. Rodríguez-Coira, Patrick Lowrance, C. J. Hailey, Thomas Ott, S. Zhang, A. Drescher, G. Ponti, Giovanni G. Fazio, Steven P. Willner, S. D. von Fellenberg, Linda J. Tacconi, Maryam Habibi, H. Bonnet, Julien Woillez, V. Lapeyrère, Sylvestre Lacour, António Amorim, Erich Wiezorrek, Xavier Haubois, Guy Perrin, J. Neilsen, K. Mori, Eric Gendron, Frank Eisenhauer, G. Heißel, Pierre Léna, Joseph L. Hora, Karine Perraut, Charles F. Gammie, Feng Gao, G. Witzel, Gérard Zins, Mark Morris, André Young, Julia Stadler, Jean-Phillipe Berger, Hope Boyce, Stefan Gillessen, Lieselotte Jochum, Roberto Abuter, High Energy Astrophys. & Astropart. Phys (API, FNWI), 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), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Accretion, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Electron, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - high energy astrophysical phenomena, law.invention, Luminosity, symbols.namesake, law, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Accretion (meteorology), Galaxy: center, 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astronomy and Astrophysics, Black hole physics, Synchrotron, ddc, Particle acceleration, Lorentz factor, 13. Climate action, Space and Planetary Science, Accretion disks, symbols, Spectral energy distribution, Flare
Abstract: We report the time-resolved spectral analysis of a bright near-infrared and moderate X-ray flare of Sgr A*. We obtained light curves in the $M$-, $K$-, and $H$-bands in the mid- and near-infrared and in the $2-8~\mathrm{keV}$ and $2-70~\mathrm{keV}$ bands in the X-ray. The observed spectral slope in the near-infrared band is $\nu L_\nu\propto \nu^{0.5\pm0.2}$; the spectral slope observed in the X-ray band is $\nu L_\nu \propto \nu^{-0.7\pm0.5}$. We tested synchrotron and synchrotron self-Compton (SSC) scenarios. The observed near-infrared brightness and X-ray faintness, together with the observed spectral slopes, pose challenges for all models explored. We rule out a scenario in which the near-infrared emission is synchrotron emission and the X-ray emission is SSC. A one-zone model in which both the near-infrared and X-ray luminosity are produced by SSC and a model in which the luminosity stems from a cooled synchrotron spectrum can explain the flare. In order to describe the mean SED, both models require specific values of the maximum Lorentz factor $\gamma_{max}$, which however differ by roughly two orders of magnitude: the SSC model suggests that electrons are accelerated to $\gamma_{max}\sim 500$, while cooled synchrotron model requires acceleration up to $\gamma_{max}\sim5\times 10^{4}$. The SSC scenario requires electron densities of $10^{10}~\mathrm{cm^{-3}}$ much larger than typical ambient densities in the accretion flow, and thus require in an extraordinary accretion event. In contrast, assuming a source size of $1R_s$, the cooled synchrotron scenario can be realized with densities and magnetic fields comparable with the ambient accretion flow. For both models, the temporal evolution is regulated through the maximum acceleration factor $\gamma_{max}$, implying that sustained particle acceleration is required to explain at least a part of the temporal evolution of the flare., Comment: accepted for publication in Astronomy & Astrophysics; preview abstract shortened due to arXiv requirements
Published: 2021
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7. GRAVITY upgrade with high-performance grisms with factor >2 enhanced throughput

Author: Guy Perrin, Alejandra Rosales, Christian Straubmeier, Odele Straub, Eckhard Sturm, Laurent Jocou, Frank Eisenhauer, Ekkehard Wieprecht, Karine Perraut, M. Riquelme, O. Pfuhl, Andreas Eckart, Tim de Zeeuw, Jinyi Shangguan, Erich Wiezorrek, M. Bauböck, António Amorim, P. Guajardo, V. Lapeyrere, C. Rau, Martin G. F. Mayer, Kateryna Kravchenko, Takashi Sukegawa, Thomas Ott, Maryam Habibi, Felix Widmann, A. Buron, F. Haussmann, Julia Stadler, Sebastiano von Fellenberg, Sylvestre Lacour, Yukinobu Okura, Wolfgang Brandner, Reinhard Genzel, L. Barl, Senol Yazici, Stefan Gillessen, Feng Gao, Thibaut Paumard, David M. Huber, Paolo Garcia, Laurent Pallanca, Tuthill, P.G., Mérand, A., and Sallum, S.
Subjects: Grism, Physics, Interferometry, Gravity (chemistry), Optics, Upgrade, Spectrometer, business.industry, Instrumentation, Astrometry, business, Throughput (business)
Abstract: During the past years, the VLTI-instrument GRAVITY has made spectacular discoveries with phase-referenced interferometric imaging with milliarcsecond resolution and ten microarcsecond astrometry. Here, we report on the upgrade of the GRAVITY science spectrometer with two new grisms in October 2019, increasing the instrument throughput by a factor > 2. This improvement was made possible by using a high refractive index Germanium substrate, which reduces the grism and groove angles, and by successfully applying an anti-reflection coating to the ruled surface to overcome Fresnel losses. We present the design, manufacturing, and laboratory testing of the new grisms, as well as the results from the re-commissioning on sky.
Published: 2021

8. The GRAVITY Young Stellar Object survey. VII. The inner dusty disks of T Tauri stars

Author: A. Drescher, S. von Fellenberg, R. Garcia-Lopez, E. F. van Dishoeck, Lucas Labadie, Gilles Duvert, Christian Straubmeier, Myriam Benisty, Th. Henning, Jerome Bouvier, Stefan Gillessen, Sylvestre Lacour, Julia Stadler, T. Taro Shimizu, Silvia Scheithauer, Felix Widmann, Eckhard Sturm, P. Garciaınst, R. Grellmann, Laurent Jocou, Paola Caselli, Evelyne Alecian, Jean-Phillipe Berger, T. Ott, Z. Hubert, V. Lapeyrère, Eric Gendron, Frank Eisenhauer, Frederic H. Vincent, J. Sanchez-Bermudez, Andreas Eckart, A. Caratti o Garatti, A. P. Sousa, Pierre Léna, António Amorim, Natascha M. Förster-Schreiber, Pierre Kervella, L. Klarmann, Odele Straub, Dieter Lutz, J.-B. Le Bouquin, Thibaut Paumard, R. Genzel, Catherine Dougados, Y.-I. Bouarour, Yann Clénet, P. T. de Zeeuw, Wolfgang Brandner, Ric Davies, Jinyi Shangguan, Matthew Horrobin, Francois Menard, G. Heissel, Karine Perraut, Linda J. Tacconi, Guy Perrin, Stefan Hippler, 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 ), and 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)
Subjects: Gravity (chemistry), Techniques: Interferometric, Young stellar object, Continuum (design consultancy), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Techniques: High Angular Resolution, Infrared: ISM, Physics, Earth and Planetary Astrophysics (astro-ph.EP), [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, Astronomy and Astrophysics, Radius, Astrophysics - Astrophysics of Galaxies, Accretion (astrophysics), Stars, T Tauri star, Instrumentation: High Angular Resolution, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Circumstellar Matter, Astrophysics::Earth and Planetary Astrophysics, Stars: Formation, Astrophysics - Earth and Planetary Astrophysics
Abstract: These protoplanetary disks in T Tauri stars play a central role in star and planet formation. We spatially resolve at sub-au scales the innermost regions of a sample of T Tauri's disks to better understand their morphology and composition. We extended our homogeneous data set of 27 Herbig stars and collected near-IR K-band observations of 17 T Tauri stars, spanning effective temperatures and luminosities in the ranges of ~4000-6000 K and ~0.4-10 Lsun. We focus on the continuum emission and develop semi-physical geometrical models to fit the interferometric data and search for trends between the properties of the disk and the central star. The best-fit models of the disk's inner rim correspond to wide rings. We extend the Radius-luminosity relation toward the smallest luminosities (0.4-10 Lsun) and find the R~L^(1/2) trend is no longer valid, since the K-band sizes measured with GRAVITY are larger than the predicted sizes from sublimation radius computation. No clear correlation between the K-band half-flux radius and the mass accretion rate is seen. Having magnetic truncation radii in agreement with the K-band GRAVITY sizes would require magnetic fields as strong as a few kG, which should have been detected, suggesting that accretion is not the main process governing the location of the half-flux radius of the inner dusty disk. Our measurements agree with models that take into account the scattered light. The N-to-K band size ratio may be a proxy for disentangling disks with silicate features in emission from disks with weak and/or in absorption silicate features. When comparing inclinations and PA of the inner disks to those of the outer disks (ALMA) in nine objects of our sample, we detect misalignments for four objects., Comment: Accepted for publication in A&A; 20 pages, 15 figures, 9 tables
Published: 2021
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9. Detection of faint stars near Sagittarius A* with GRAVITY

Author: Christian Straubmeier, Stefan Hippler, Th. Henning, Feng Gao, Gérard Zins, Maryam Habibi, Linda J. Tacconi, Oliver Pfuhl, V. Lapeyrère, Xavier Haubois, Guy Perrin, A. Jiménez-Rosales, Felix Widmann, G. Heißel, António Amorim, Stefan Gillessen, Yann Clénet, P. T. de Zeeuw, H. Bonnet, Jason Dexter, Paulo J. V. Garcia, Julien Woillez, Ric Davies, Lieselotte Jochum, Eric Gendron, G. Rodríguez-Coira, Eckhard Sturm, Laurent Jocou, Jinyi Shangguan, S. Yazici, T. Taro Shimizu, Thibaut Paumard, M. Nowak, M. Bauböck, Karine Perraut, Reinhard Genzel, N. M. Förster Schreiber, Wolfgang Brandner, Matthew Horrobin, Julia Stadler, Thomas Ott, Idel Waisberg, A. Drescher, S. von Fellenberg, Sebastian Rabien, Ekkehard Wieprecht, F. Vincent, Pierre Kervella, Jean-Philippe Berger, Odele Straub, Dieter Lutz, J.-B. Le Bouquin, Sylvestre Lacour, Silvia Scheithauer, Y. Dallilar, Andreas Kaufer, Frank Eisenhauer, Pierre Léna, Erich Wiezorrek, Roberto Abuter, 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), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and GRAVITY
Subjects: Astrophysics - instrumentation and methods for astrophysics, Stars: imaging, Proper motion, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics - astrophysics of galaxies, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Supermassive black hole, Galaxy: center, 010308 nuclear & particles physics, Galactic Center, Astronomy and Astrophysics, Infrared: stars, Stars, Sagittarius A, 13. Climate action, Space and Planetary Science, Magnitude (astronomy), Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Radio astronomy, Gravitational redshift
Abstract: International audience; The spin of the supermassive black hole that resides at the Galactic Center can, in principle, be measured by accurate measurements of the orbits of stars that are much closer to Sgr A* than S2, the orbit of which recently provided the measurement of the gravitational redshift and the Schwarzschild precession. The GRAVITY near-infrared interferometric instrument combining the four 8m telescopes of the VLT provides a spatial resolution of 2–4 mas, breaking the confusion barrier for adaptive-optics-assisted imaging with a single 8–10m telescope. We used GRAVITY to observe Sgr A* over a period of six months in 2019 and employed interferometric reconstruction methods developed in radio astronomy to search for faint objects near Sgr A*. This revealed a slowly moving star of magnitude 18.9 in the K-band within 30 mas of Sgr A*. The position and proper motion of the star are consistent with the previously known star S62, which is at a substantially greater physical distance, but in projection passes close to Sgr A*. Observations in August and September 2019 detected S29 easily, with K-magnitude of 16.6, at approximately 130 mas from Sgr A*. The planned upgrades of GRAVITY, and further improvements in the calibration, offer greater chances of finding stars fainter than K-magnitude of 19.Key words: Galaxy: center / stars: imaging / infrared: stars⋆ GRAVITY was developed as part of a collaboration by the Max Planck Institute for extraterrestrial Physics, LESIA of the Observatoire de Paris/Université PSL/CNRS/Sorbonne Université/Université de Paris and IPAG of Université Grenoble Alpes/CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the CENTRA – Centro de Astrofisica e Gravitação, and the European Southern Observatory.⋆⋆ Corresponding authors: F. Gao, e-mail: fgao@mpe.mpg.de; T. Paumard, e-mail: thibaut.paumard@obspm.fr
Published: 2021
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10. Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*

Author: Feng Gao, P. T. de Zeeuw, Julia Stadler, Maryam Habibi, Y. Dallilar, M. Bauböck, A. Jiménez-Rosales, Jason Dexter, T. Ott, Frank Eisenhauer, Alexander Tchekhovskoy, Reinhard Genzel, A. Drescher, S. von Fellenberg, Felix Widmann, Stefan Gillessen, S M Ressler, and Odele Straub
Subjects: Accretion, Photon, MHD, General relativity, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, 01 natural sciences, Polarization, 0103 physical sciences, Radiative transfer, 010303 astronomy & astrophysics, Spin-½, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Ring (mathematics), 010308 nuclear & particles physics, Linear polarization, Astronomy and Astrophysics, Black hole physics, Polarization (waves), Computational physics, Black hole, Space and Planetary Science, Relativistic quantum chemistry, Astrophysics - High Energy Astrophysical Phenomena, Accretion discs
Abstract: Using general relativistic magnetohydrodynamic simulations of accreting black holes, we show that a suitable subtraction of the linear polarization per pixel from total intensity images can enhance the photon ring features. We find that the photon ring is typically a factor of $\simeq 2$ less polarized than the rest of the image. This is due to a combination of plasma and general relativistic effects, as well as magnetic turbulence. When there are no other persistently depolarized image features, adding the subtracted residuals over time results in a sharp image of the photon ring. We show that the method works well for sample, viable GRMHD models of Sgr A* and M87*, where measurements of the photon ring properties would provide new measurements of black hole mass and spin, and potentially allow for tests of the "no-hair" theorem of general relativity., Comment: 13 pages, 12 figures, accepted for publication in MNRAS
Published: 2021

11. The GRAVITY Young Stellar Object survey VIII. Gas and dust faint inner rings in the hybrid disk of HD141569

Author: R. Grellmann, O. Pfuhl, V. Ganci, Eric Gendron, Feng Gao, Stefan Hippler, V. Coudé du Foresto, Guy Perrin, Gérard Rousset, Thibaut Paumard, Frederic H. Vincent, Catherine Dougados, A. Wojtczak, R. Genzel, A. Drescher, A. de Valon, Lucas Labadie, Gilles Duvert, E. F. van Dishoeck, G. Heissel, S. D. von Fellenberg, V. Lapeyrère, Mercedes E. Filho, Christian Straubmeier, Karine Perraut, Julia Stadler, Th. Henning, Paola Caselli, Felix Widmann, Z. Hubert, Stefan Gillessen, Matthew Horrobin, António Amorim, Odele Straub, R. Garcia Lopez, J.-B. Le Bouquin, L. Klarmann, Paulo J. V. Garcia, Jean-Phillipe Berger, G. Heißel, J. Sanchez-Bermudez, Andreas Eckart, Pierre Kervella, Silvia Scheithauer, Sylvestre Lacour, T. Ott, Frank Eisenhauer, Pierre Léna, T. Taro Shimizu, M. Bauböck, A. Caratti o Garatti, A. Jiménez-Rosales, Myriam Benisty, F. Eupen, Julien Woillez, Eckhard Sturm, Laurent Jocou, Wolfgang Brandner, Yann Clénet, P. T. de Zeeuw, and Jinyi Shangguan
Subjects: Physics, Protoplanetary disks, Earth and Planetary Astrophysics (astro-ph.EP), Young stellar object, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Planetary system, Stars, Infrared: planetary systems, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Techniques: interferometric, Radiative transfer, Spectral energy distribution, Astrophysics::Solar and Stellar Astrophysics, Emission spectrum, Astrophysics::Earth and Planetary Astrophysics, Spectral resolution, Stars: individual: HD 141569, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Line (formation), Astrophysics - Earth and Planetary Astrophysics
Abstract: The formation and evolution of planetary systems impact the primordial accretion disk. HD141569 is the only known pre-main sequence star characterized by a hybrid disk. Observations probed the outer-disk structure showing a complex system of rings and interferometric observations attempted to characterize its inner 5 au region, but derived limited constraints. The goal of this work was to explore with new high-resolution interferometric observations the properties of the dust and gas in the internal regions of HD141569. We observed HD141569 on mas scales with GRAVITY/VLTI in the near-infrared at low and high spectral resolution. We interpreted the visibilities and spectral energy distribution with geometrical models and radiative transfer techniques to constrain the dust emission. We analyzed the high spectral resolution quantities to investigate the properties of the Br-Gamma line emitting region. Thanks to the combination of three different epochs, GRAVITY resolves the inner dusty disk in the K band. Data modeling shows that an IR excess of about 6% is spatially resolved and that the origin of this emission is confined in a ring of material located at a radius of 1 au from the star with a width smaller than 0.3 au. The MCMax modeling suggests that this emission could originate from a small amount of QHPs, while large silicate grain models cannot reproduce at the same time the observational constraints on the properties of near-IR and mid-IR fluxes. The differential phases in the Br-Gamma line clearly show an S-shape that can be best reproduced witha gas disk in Keplerian rotation, confined within 0.09 au. This is also hinted at by the double-peaked Br-Gamma emission line shape. The modeling of the continuum and gas emission shows that the inclination and position angle of these two components are consistent with a system showing relatively coplanar rings on all scales., Comment: Accepted for publication in A&A; 25 pages, 15 figures, 5 tables
Published: 2021
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12. MOLsphere and pulsations of the Galactic Center’s red supergiant GCIRS 7 from VLTI/GRAVITY

Author: Karine Perraut, Xavier Haubois, Jason Dexter, Christian Straubmeier, Th. Henning, F. H. Vincent, Linda J. Tacconi, Eckhard Sturm, Idel Waisberg, Stefan Hippler, Guy Perrin, Vincent Lapeyrere, J. Sanchez-Bermudez, Felix Widmann, Andreas Kaufer, Thomas Ott, A. Drescher, O. Pfuhl, Julien Woillez, G. Rodríguez-Coira, Laurent Jocou, Jean-Philippe Berger, Eric Gendron, Lieselotte Jochum, Gérard Zins, S. von Fellenberg, Paulo J. V. Garcia, Sylvestre Lacour, Stefan Gillessen, M. Nowak, N. M. Förster Schreiber, Julia Stadler, Matthew Horrobin, Feng Gao, António Amorim, Frank Eisenhauer, Pierre Léna, Odele Straub, J.-B. Le Bouquin, Erich Wiezorrek, M. Habibi, Reinhard Genzel, Silvia Scheithauer, H. Bonnet, Thibaut Paumard, Pierre Kervella, A. Jiménez-Rosales, Andreas Eckart, Ekkehard Wieprecht, S. Yazici, T. Taro Shimizu, M. Bauböck, Roberto Abuter, Jinyi Shangguan, Wolfgang Brandner, Yann Clénet, P. T. de Zeeuw, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), 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), Département de Chimie Moléculaire - Ingéniérie et Intéractions BioMoléculaires (DCM - I2BM), Département de Chimie Moléculaire (DCM), Université Grenoble Alpes (UGA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Extraterrestrische Physik (MPE), 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), Wageningen University and Research [Wageningen] (WUR), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Poznan Technical University, Max Planck Institute for Astronomy (MPIA), GRAVITY Collaboration, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics [LESIA], Récepteurs nucléaires, maladies cardiovasculaires et diabète - U 1011 [RNMCD], Département de Chimie Moléculaire - Ingéniérie et Intéractions BioMoléculaires [DCM - I2BM], Max-Planck-Institut für Extraterrestrische Physik [MPE], Laboratoire d'études spatiales et d'instrumentation en astrophysique [LESIA], Wageningen University and Research [Wageningen] [WUR], European Southern Observatory [Santiago] [ESO], European Southern Observatory [ESO], Institut Européen des membranes [IEM], Institut de Planétologie et d'Astrophysique de Grenoble [IPAG], Max Planck Institute for Astronomy [MPIA], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Universidade de Lisboa = University of Lisbon (ULISBOA), Centro de Astrofísica e Gravitação (CENTRA), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, 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, Leiden University, University of Colorado [Boulder], Universität zu Köln = University of Cologne, Max Planck Institute for Radio Astronomy, Universidade do Porto = University of Porto, University of California [Berkeley] (UC Berkeley), University of California (UC), Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), Weizmann Institute of Science [Rehovot, Israël], Sciences, EDP, Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut Européen des membranes (IEM), and Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Galaxy: nucleus, techniques: interferometric, stars: individual: GCIRS 7, stars: fundamental parameters, supergiants, Astrophysics - astrophysics of galaxies, Extinction (astronomy), Continuum (design consultancy), FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, Astrophysics - solar and stellar astrophysics, 0103 physical sciences, Red supergiant, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, Photosphere, 010308 nuclear & particles physics, Galactic Center, Astronomy and Astrophysics, Stars, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Supergiant, [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: GCIRS 7, the brightest star in the Galactic central parsec, formed $6\pm2$ Myr ago together with dozens of massive stars in a disk orbiting the central black-hole. It has been argued that GCIRS 7 is a pulsating body, on the basis of photometric variability. We present the first medium-resolution ($R=500$), K-band spectro-interferometric observations of GCIRS 7, using the GRAVITY instrument with the four auxiliary telescopes of the ESO VLTI. We looked for variations using two epochs, namely 2017 and 2019. We find GCIRS 7 to be moderately resolved with a uniform-disk photospheric diameter of $\theta^*_\text{UD}=1.55 \pm 0.03$ mas ($R^*_\text{UD}=1368 \pm 26$ $R_\odot$) in the K-band continuum. The narrow-band uniform-disk diameter increases above 2.3 $\mu$m, with a clear correlation with the CO band heads in the spectrum. This correlation is aptly modeled by a hot ($T_\text{L}=2368\pm37$ K), geometrically thin molecular shell with a diameter of $\theta_\text{L}=1.74\pm0.03$ mas, as measured in 2017. The shell diameter increased ($\theta_\text{L}=1.89\pm0.03$ mas), while its temperature decreased ($T_\text{L}=2140\pm42$ K) in 2019. In contrast, the photospheric diameter $\theta^*_\text{UD}$ and the extinction up to the photosphere of GCIRS 7 ($A_{\mathrm{K}_\mathrm{S}}=3.18 \pm 0.16$) have the same value within uncertainties at the two epochs. In the context of previous interferometric and photo-spectrometric measurements, the GRAVITY data allow for an interpretation in terms of photospheric pulsations. The photospheric diameter measured in 2017 and 2019 is significantly larger than previously reported using the PIONIER instrument ($\theta_*=1.076 \pm 0.093$ mas in 2013 in the H band). The parameters of the photosphere and molecular shell of GCIRS 7 are comparable to those of other red supergiants that have previously been studied using interferometry., Comment: 12 pages, 11 figures, 3 tables. Accepted for publication in Astronomy and Astrophysics (A&A)
Published: 2021
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13. The mass of β Pictoris c from β Pictoris b orbital motion

Author: Matthias Samland, Anne-Lise Maire, David Mouillet, Andreas Eckart, Valentin Christiaens, Julien Woillez, Sarah Blunt, K. Perraut, T. Paumard, T. Ott, Myriam Benisty, E. Nasedkin, A. Mérand, Z. Hubert, Stefan Hippler, Frank Eisenhauer, Roderick Dembet, Gilles Otten, F. H. Vincent, Pierre Léna, Jinyi Shangguan, Miriam Keppler, Ekkehard Wieprecht, G. Bourdarot, M. Houllé, Odele Straub, Alexander J. Bohn, M. Nowak, Felix Widmann, K. Ward-Duong, P. T. de Zeeuw, J.-B. Le Bouquin, Julia Stadler, T. Taro Shimizu, A. Boccaletti, David K. Sing, Ji Wang, Linda J. Tacconi, Arthur Vigan, Elodie Choquet, Jens Kammerer, Claudia Paladini, J. Rameau, R. J. García López, Xavier Haubois, E. Rickman, Guy Perrin, J. P. Berger, Wolfgang Brandner, Eric Gendron, G. Heißel, H. Bonnet, Laurent Jocou, A. Cridland, S. D. von Fellenberg, Pierre Kervella, R. Asensio-Torres, G. Rousset, O. Pfuhl, Erich Wiezorrek, M. Bonnefoy, Y. Clénet, Senol Yazici, R. Abuter, John D. Monnier, Laura Kreidberg, Paulo J. V. Garcia, Zafar Rustamkulov, Tomas Stolker, Gilles Duvert, Paul Mollière, H. Beust, Eckhard Sturm, António Amorim, Anne-Marie Lagrange, Paola Caselli, Christian Straubmeier, Th. Henning, G. Chauvin, Benjamin Charnay, Sylvestre Lacour, E. F. van Dishoeck, Jason Dexter, Stefan Gillessen, André Young, D. Lutz, V. Coudé du Foresto, R. Genzel, Feng Gao, J. H. Girard, Faustine Cantalloube, L. Rodet, Sasha Hinkley, A. Drescher, Vincent Lapeyrere, Laurent Pueyo, Matthew Horrobin, M. L. Bolzer, Institut des Sciences Chimiques de Rennes (ISCR), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), 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), MacoPharma, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Caltech Department of Astronomy [Pasadena], California Institute of Technology (CALTECH), Departamento de Astronomía, Universidad de Chile = University of Chile [Santiago] (UCHILE), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, European Southern Observatory (ESO), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Max-Planck-Institut für Astronomie (MPIA), 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), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Service de Pathologie respiratoire et allergologie [CHU Limoges], CHU Limoges, University of Auckland [Auckland], the GRAVITY Collaboration, Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (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, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Harvard University-Smithsonian Institution, and Université de Genève = University of Geneva (UNIGE)
Subjects: Astrophysics - instrumentation and methods for astrophysics, planets and satellites: detection, 010504 meteorology & atmospheric sciences, Astrophysics, Astrophysics - Earth and planetary astrophysics, 01 natural sciences, High angular resolution, Planet, instrumentation: high angular resolution, 0103 physical sciences, Beta Pictoris, 10. No inequality, instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation, 0105 earth and related environmental sciences, Orbital elements, Physics, Interferometers, Astronomy and Astrophysics, Astrometry, Exoplanet, Radial velocity, Detection, Space and Planetary Science, Orbital motion, Planets and satellites, Eccentricity (mathematics), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Aims.We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet.Methods.We combined previous astrometry ofβPictoris b with a new set of observations from the GRAVITY interferometer. The orbital motion ofβPictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet,βPictoris c, was also reobserved at a separation of 96 mas, confirming the previous orbital estimations.Results.From the astrometry of planet b only, we can (i) detect the presence ofβPictoris c and (ii) constrain its mass to 10.04−3.10+4.53MJup. If one adds the astrometry ofβPictoris c, the mass is narrowed down to 9.15−1.06+1.08MJup. The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to 8.89−0.75+0.75MJup. With a semimajor axis of 2.68 ± 0.02 au, a period of 1221 ± 15 days, and an eccentricity of 0.32 ± 0.02, the orbital parameters ofβPictoris c are now constrained as precisely as those ofβPictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets’ dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet.
Published: 2021
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14. Improved GRAVITY astrometric accuracy from modeling of optical aberrations

Author: Stefan Hippler, Maryam Habibi, S. Yazici, Paulo J. V. Garcia, T. Taro Shimizu, Roberto Abuter, F. Vincent, Linda J. Tacconi, M. Bauböck, Pierre Kervella, Guy Perrin, Idel Waisberg, G. Heißel, Karine Perraut, Eckhard Sturm, Laurent Jocou, Lieselotte Jochum, Sebastian Rabien, Julien Woillez, A. Jiménez-Rosales, Gérard Zins, M. Nowak, Odele Straub, Dieter Lutz, J.-B. Le Bouquin, Ekkehard Wieprecht, Julia Stadler, Reinhard Genzel, Wolfgang Brandner, Feng Gao, Thomas Ott, A. Drescher, N. M. Förster Schreiber, S. von Fellenberg, Christian Straubmeier, Silvia Scheithauer, Ric Davies, Y. Dallilar, Th. Henning, H. Bonnet, Jinyi Shangguan, Eric Gendron, Andreas Eckart, Yann Clénet, P. T. de Zeeuw, Thibaut Paumard, Jason Dexter, Andreas Kaufer, Felix Widmann, Frank Eisenhauer, Pierre Léna, V. Lapeyrère, Xavier Haubois, Erich Wiezorrek, Matthew Horrobin, Sylvestre Lacour, António Amorim, Jean-Philippe Berger, G. Rodríguez-Coira, Oliver Pfuhl, Stefan Gillessen, André Young, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Astrophysics - instrumentation and methods for astrophysics, Field (physics), Astrophysics - astrophysics of galaxies, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, 010309 optics, Telescope, law, Methods: data analysis, 0103 physical sciences, Binary star, Calibration, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Physics, Galaxy: center, Galactic Center, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Astrometry, Galaxy: fundamental parameters, Interferometry, Space and Planetary Science, Instrumentation: interferometers, Astrophysics of Galaxies (astro-ph.GA), Instrumentation: high angular resolution, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: The GRAVITY instrument on the ESO VLTI pioneers the field of high-precision near-infrared interferometry by providing astrometry at the 10−100 μas level. Measurements at this high precision crucially depend on the control of systematic effects. We investigate how aberrations introduced by small optical imperfections along the path from the telescope to the detector affect the astrometry. We develop an analytical model that describes the effect of these aberrations on the measurement of complex visibilities. Our formalism accounts for pupil-plane and focal-plane aberrations, as well as for the interplay between static and turbulent aberrations, and it successfully reproduces calibration measurements of a binary star. The Galactic Center observations with GRAVITY in 2017 and 2018, when both Sgr A* and the star S2 were targeted in a single fiber pointing, are affected by these aberrations at a level lower than 0.5 mas. Removal of these effects brings the measurement in harmony with the dual-beam observations of 2019 and 2020, which are not affected by these aberrations. This also resolves the small systematic discrepancies between the derived distance R0 to the Galactic Center that were reported previously.
Published: 2021
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15. Static phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distanceStatic phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distance

Author: M. Nowak, Reinhard Genzel, Wolfgang Brandner, K. Rousselet-Perraut, Julien Woillez, Christian Straubmeier, Eckhard Sturm, Sylvestre Lacour, Felix Widmann, Sebastiano von Fellenberg, M. Bauböck, Guy Perin, Jinyi Shangguan, Odele Straub, Frank Eisenhauer, A. Jiménez-Rosales, Paulo J. V. Garcia, António Amorim, Stefan Gillessen, Julia Stadler, Feng Gao, O. Pfuhl, and Thomas Ott
Subjects: Physics, Gravity (chemistry), business.industry, Zernike polynomials, Galactic Center, Phase (waves), Astrometry, Interferometry, symbols.namesake, Optics, Optical path, symbols, Calibration, business
Abstract: The GRAVITY instrument has revolutionized optical/IR interferometry: fringe-tracking and phase-referencing allow for 30 micro-arcsecond astrometry in a dual beam mode, and for spectro-differential astrometry better than 10 micro-arcseconds. The control of systematic effects is essential to fully exploit this technological advancement. Among those systematics are static phase aberrations, introduced along the instrument's optical path, which in particular affect the inferred separation of two unresolved objects within the same FOV. Here, we present how the aberrations can be measured, characterized by low-order Zernike polynomials and, most importantly, how their impact on the astrometry is corrected. The resulting astrometry corrections are verified with calibration observations of a binary before we discuss how they affect GRAVITY's measurement of the galactic center distance.
Published: 2020
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16. First four telescopes large-separation off-axis fringe-tracking interferometry with GRAVITY at the VLTI

Author: Jinyi Shangguan, Feng Gao, Wolfgang Brandner, Frank Eisenhauer, F. Haussmann, Thomas Ott, Guy Perrin, Christian Straubmeier, Pierre Bourget, Frédéric Gonté, Eckhard Sturm, Michael Hartl, Roderick Dembet, Antonia Drescher, Sebastiano von Fellenberg, Nicolas Schuhler, Stefan Gillessen, Jürgen Ott, Gérard Zins, Julien Woillez, Paulo J. V. Garcia, O. Pfuhl, Thibaut Paumard, Karine Perraut, Michi Bauboeck, Odele Straub, Mari Lena Bolzer, Reinhard Genzel, Dieter Lutz, Felix Widmann, António Amorim, Julia Stadler, A. Jiménez-Rosales, Taro Shimizu, Bruno Chazelas, and Matthew Horrobin
Subjects: Physics, Very Large Telescope, Galactic Center, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Quasar, Astrophysics::Cosmology and Extragalactic Astrophysics, Tracking (particle physics), Redshift, Interferometry, Palomar Testbed Interferometer, Astronomical interferometer, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We present the successful demonstration of world's first large-separation ~30" off-axis fringe tracking with four telescopes in October 2019. With this technique we increase the sky-coverage for optical interferometry by orders of magnitude compared to current technology. Following the early work at the Palomar Testbed Interferometer, the first demonstration of off-axis fringe tracking at the Keck Interferometer and with PRIMA at the ESO Very Large Telescope Interferometer, and the breakthrough with the GRAVITY Galactic Center observations, we enhanced the VLTI infrastructure for GRAVITY to take advantage of the PRIMA Star separators and Differential Delay Lines for off-axis fringe tracking. In our presentation we give an introduction to the subject, present the enhancements of the VLTI, and present our results from the first on-sky operation in October 2019, with observations of the Orion Trapezium Cluster, a field brown dwarf, and a high redshift quasar.
Published: 2020
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17. Polarization analysis of GRAVITY and the VLTI

Author: Feng Gao, Christian Straubmeier, Nicolas Schuhler, O. Pfuhl, António Amorim, Jinyi Shangguan, M. Bauböck, Paulo J. V. Garcia, Eckhard Sturm, Jason Dexter, Wolfgang Brandner, Sylvestre Lacour, K. Rousselet-Perraut, Stefan Gillessen, Guy Perrin, Sebastiano von Fellenberg, Thomas Ott, Felix Widmann, A. Jiménez-Rosales, Xavier Haubois, Frank Eisenhauer, Odele Straub, and Reinhard Genzel
Subjects: Physics, Brewster's angle, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics, Polarization (waves), law.invention, General Relativity and Quantum Cosmology, symbols.namesake, Interferometry, law, symbols, Astrophysics::Solar and Stellar Astrophysics, Flare
Abstract: Instrumental polarization can have large effects on measurements with the VLTI, as it can alter measured polarization and introduce uncertainties. To understand these effects we measured and simulated the instrumental polarization of the VLTI and of GRAVITY. We are able to provide a calibration model for GRAVITY observations and quantify systematic uncertainties due to instrumental polarization. This work has shown to be crucial to measure the polarization of the galactic center black hole Sgr A* where we detect a swing in the polarization angle during flare events. While the analysis was done for GRAVITY, it also gives an important basis for the design of future near-infrared instruments at the VLTI.
Published: 2020
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18. The GRAVITY young stellar object survey: III. The dusty disk of RY Lup

Author: Christian Straubmeier, V. Coudé du Foresto, T. Ott, Th. Henning, Guy Perrin, Z. Hubert, Frank Eisenhauer, E. F. van Dishoeck, Pierre Léna, Mercedes E. Filho, Stefan Hippler, Yann Clénet, P. T. de Zeeuw, O. Pfuhl, Odele Straub, J.-B. Le Bouquin, A. Caratti o Garatti, Karine Perraut, F. Vincent, Pierre Kervella, Eckhard Sturm, Julia Stadler, Feng Gao, Laurent Jocou, Catherine Dougados, Jinyi Shangguan, R. Genzel, R. Garcia-Lopez, M. Wiest, Thibaut Paumard, Gilles Duvert, Paola Caselli, Wing-Fai Thi, Wolfgang Brandner, Y.-I. Bouarour, Silvia Scheithauer, R. Grellmann, Francois Menard, S. D. von Fellenberg, Paulo J. V. Garcia, Stefan Gillessen, F. Eupen, Sylvestre Lacour, J. Sanchez-Bermudez, Andreas Eckart, Eric Gendron, A. Natta, Felix Widmann, Matthew Horrobin, Jean-Phillipe Berger, A. Jiménez-Rosales, L. Klarmann, Myriam Benisty, M. Bauböck, António Amorim, Lucas Labadie, Gérard Rousset, 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), Laboratoire Franco-Chilien d'Astronomie (LFCA), Universidad de Concepción [Chile]-Pontificia Universidad Católica de Chile (UC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Universidad de Chile, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Physikalisches Institut [Köln], Universität zu Köln, Faculty of Agronomy, University of Parakou, European Southern Observatory (ESO), SIM/IDL Faculdade de Ciências da Universidade de Lisboa (FCUL), University of Lisboa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Extraterrestrial Physics (MPE), University of Brasilia [Brazil] (UnB), Universitat Politècnica de València (UPV), Galaxies, Etoiles, Physique, Instrumentation (GEPI), 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), Laboratoire Transport et Environnement (INRETS/LTE), Institut National de Recherche sur les Transports et leur Sécurité (INRETS), Swedish Space Corporation (SSC), HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH UFZ HALLE SUR SAALE DEU, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), GRAVITY Collaboration, 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, 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 [2007-2019] (Grenoble INP [2007-2019])-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 [2007-2019] (Grenoble INP [2007-2019])-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]), Centre National de la Recherche Scientifique (CNRS)-Universidad de Concepción [Chile]-Pontificia Universidad Católica de Chile (UC)-Universidad de Chile-Institut national des sciences de l'Univers (INSU - CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble [2020-....] (OSUG [2020-....]), 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 [2020-....] (UGA [2020-....])-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 [2020-....] (UGA [2020-....]), Environnement Ville Société (EVS), École normale supérieure - Lyon (ENS Lyon)-École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet [Saint-Étienne] (UJM)-École Nationale des Travaux Publics de l'État (ENTPE)-École nationale supérieure d'architecture de Lyon (ENSAL)-Centre National de la Recherche Scientifique (CNRS), Universitat Politecnica de Valencia (UPV), and 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)
Subjects: Young stellar object, variables, Extinction (astronomy), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: pre-main sequence, Herbig Ae/Be -stars, T Tauri, 01 natural sciences, circumstellar matter, Luminosity, stars: low-mass, stars: individual: RY Lup, protoplanetary disks -stars, 0103 physical sciences, low-mass, Astrophysics::Solar and Stellar Astrophysics, individual, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, stars: variables: T Tauri, Very Large Telescope, 010308 nuclear & particles physics, protoplanetary disks, Herbig Ae/Be, Astronomy and Astrophysics, Radius, Effective temperature, Astrophysics - Astrophysics of Galaxies, T Tauri star, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), pre-main sequencestars, Spectral energy distribution, Astrophysics::Earth and Planetary Astrophysics, RY Lup -circumstellar matter -stars, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8m telescopes. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the Spectral Energy Distribution and match the interferometric observations. To match the SED , our model requires a stellar luminosity of 2.5 Lsun, higher than any previously determined values. Such a high value is needed to accommodate the circumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29 Rsun. These revised fundamental parameters, when combined with the mass estimates available , lead to an age of 0.5-2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our disk model nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones. We derive an inner rim location at 0.12~au from the central star. This model corresponds to an inclination of the inner disk of 50deg, which is in mild tension with previous determinations of a more inclined outer disk from SPHERE (70 deg in NIR) and ALMA(67 $\pm$5 deg) images, but consistent with the inclination determination from the ALMA CO spectra (55$\pm$5deg). Increasing the inclination of the inner disk to 70 deg leads to a higher line-of-sight extinction and therefore requires a higher stellar luminosity of 4.65 Lsun to match the observed flux levels. This luminosity would translate to a stellar radius of 3.13~Rsun, leading to an age of 2-3~Ma, and a stellar mass of about 2 Msun, in disagreement with the observed dynamical mass estimate of 1.3-1.5 Msun. Critically, this high-inclination inner disk model also fails to reproduce the visibilities observed with GRAVITY., Accepted for publication in A&A; 11 pages, 5 figures, 3 tables
Published: 2020
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19. Direct confirmation of the radial-velocity planet β Pictoris c

Author: Benjamin Charnay, Feng Gao, Antoine Mérand, L. Rodet, H. Bonnet, Tyler Gardner, Jean-Phillipe Berger, E. F. van Dishoeck, Anthony Boccaletti, Stefan Gillessen, Felix Widmann, Eric Gendron, Hervé Beust, Karine Perraut, Wolfgang Brandner, A. Cridland, J. Rameau, Sasha Hinkley, R. Asensio-Torres, Stefan Hippler, Roderick Dembet, Thibaut Paumard, John D. Monnier, Claudia Paladini, Valentin Christiaens, Julien Woillez, Linda J. Tacconi, Gilles Otten, Z. Hubert, V. Lapeyrère, Xavier Haubois, António Amorim, Guy Perrin, Jinyi Shangguan, Jingxiu Wang, R. Garcia Lopez, David Mouillet, Erich Wiezorrek, M. Nowak, Reinhard Genzel, Sylvestre Lacour, P. Rubini, G. Heißel, Gilles Duvert, Odele Straub, J.-B. Le Bouquin, Thomas Ott, Jens Kammerer, Anne-Lise Maire, A. Drescher, Laura Kreidberg, G. Rodríguez-Coira, O. Pfuhl, Paulo J. V. Garcia, Laurent Pueyo, A. Grandjean, Frank Eisenhauer, Yann Clénet, P. T. de Zeeuw, Pierre Léna, Matthew Horrobin, V. Coudé du Foresto, Roberto Abuter, Anne-Marie Lagrange, S. D. von Fellenberg, Tomas Stolker, Gérard Rousset, F. Vincent, Pierre Kervella, Faustine Cantalloube, Julien Girard, Andreas Eckart, Arthur Vigan, Mickael Bonnefoy, Paul Mollière, Silvia Scheithauer, André Müller, Miriam Keppler, Ekkehard Wieprecht, E. Nasedkin, Christian Straubmeier, Th. Henning, Jason Dexter, Sarah Blunt, Myriam Benisty, M. Houllé, K. Ward-Duong, Julia Stadler, A. Jiménez-Rosales, Eckhard Sturm, Laurent Jocou, M. Kulikauskas, M. Bauböck, Elodie Choquet, 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), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), and 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)
Subjects: planets and satellites, Astrophysics, 01 natural sciences, Luminosity, formation -techniques, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, detection -planets and satellites, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Planetary core, Giant planet, Astronomy and Astrophysics, Orbital period, Exoplanet, Accretion (astrophysics), Radial velocity, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], interferometric, Astrophysics::Earth and Planetary Astrophysics
Abstract: Context.Methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. Indirect methods are more sensitive to planets with a small orbital period, whereas direct detection is more sensitive to planets orbiting at a large distance from their host star. This dichotomy makes it difficult to combine the two techniques on a single target at once.Aims.Simultaneous measurements made by direct and indirect techniques offer the possibility of determining the mass and luminosity of planets and a method of testing formation models. Here, we aim to show how long-baseline interferometric observations guided by radial-velocity can be used in such a way.Methods.We observed the recently-discovered giant planetβPictoris c with GRAVITY, mounted on the Very Large Telescope Interferometer.Results.This study constitutes the first direct confirmation of a planet discovered through radial velocity. We find that the planet has a temperature ofT = 1250 ± 50 K and a dynamical mass ofM = 8.2 ± 0.8 MJup. At 18.5 ± 2.5 Myr, this putsβPic c close to a ‘hot start’ track, which is usually associated with formation via disk instability. Conversely, the planet orbits at a distance of 2.7 au, which is too close for disk instability to occur. The low apparent magnitude (MK = 14.3 ± 0.1) favours a core accretion scenario.Conclusions.We suggest that this apparent contradiction is a sign of hot core accretion, for example, due to the mass of the planetary core or the existence of a high-temperature accretion shock during formation.
Published: 2020
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20. Unveiling the β Pictoris system, coupling high contrast imaging, interferometric, and radial velocity data

Author: Christian Straubmeier, J. Hagelberg, Anne-Marie Lagrange, A. Grandjean, Frank Eisenhauer, Myriam Benisty, Silvano Desidera, R. Asensio-Torres, Anne-Lise Maire, M. Nowak, Thibaut Paumard, F. Cantalloube, Jens Kammerer, Yann Clénet, P. T. de Zeeuw, Matthew Horrobin, Karine Perraut, Eric Gendron, O. Pfuhl, L. Pueyo, Stefan Gillessen, Stefan Hippler, John Monnier, Raphael Galicher, P. Thebault, Gael Chauvin, C. Babusiaux, J. Wang, Wolfgang Brandner, L. Kreidberg, P. Léna, V. Lapeyrère, J. M. Girard, Sylvestre Lacour, G. Rodríguez-Coira, Guy Perrin, Matthew A. Kenworthy, H. Le Coroller, G. Heissel, F. Galland, V. Christiaens, P. Delorme, V. Coudé du Foresto, E. Choquet, Matthias Samland, Hervé Beust, Miriam Keppler, Odele Straub, Mickael Bonnefoy, Gilles Duvert, Andreas Eckart, Z. Wahhaj, T. Stolker, A. Zurlo, C. Paladini, F. Vincent, G. Otten, M. Janson, O. Flasseur, J.-B. Le Bouquin, A. Mérand, Felix Widmann, G. Rousset, Jinyi Shangguan, N. Meunier, Feng Gao, R. Gratton, A. Vigan, Paul Mollière, Jean-Phillipe Berger, P. Rubini, P. Kervella, T. Henning, António Amorim, T. Schmidt, Julien Woillez, Xavier Haubois, Anthony Boccaletti, Maud Langlois, Q. Kral, P. Garcia, Thomas Ott, L. Rodet, B. Charnay, R. Garcia Lopez, Reinhard Genzel, Sergio Messina, 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 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)-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, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), 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), 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), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), CENTRA-SIM, IDL-Faculdade de Ciencias da Universidade de Lisboa, Departamento de Astronomía, Universidad de Chile = University of Chile [Santiago] (UCHILE), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire des Combustibles Uranium (LCU), Service d'Analyses, d'Elaboration, d'Expérientations et d'Examens des combustibles (SA3E), Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / 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-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Physikalisches Institut [Köln], Universität zu Köln = University of Cologne, Max-Planck-Institut für Astronomie (MPIA), University of Freiburg [Freiburg], Space Telescope Science Institute (STSci), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), the GRAVITY Collaboration, 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), 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), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre d'Immunologie de Marseille - Luminy (CIML), Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Observatoire de Paris - Site de Paris (OP), Universität zu Köln, 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), Institut de Recherche pour le Développement (IRD), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: planets and satellites: detection, media_common.quotation_subject, Context (language use), Astrophysics, 01 natural sciences, Planet, radial velocities -planets and satellites, 0103 physical sciences, techniques: radial velocities, Astrophysics::Solar and Stellar Astrophysics, Eccentricity (behavior), 10. No inequality, planets and satellites: fundamental parameters, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, Orbital elements, Physics, [PHYS]Physics [physics], detectionplanets and satellites, 010308 nuclear & particles physics, high angular resolution -techniques, Giant planet, techniques: high angular resolution, Astronomy and Astrophysics, Astrometry, Planetary system, Radial velocity, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], techniques, fundamental parameters
Abstract: Context. The nearby and young β Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution. Aims. We aim to further constrain the orbital and physical properties of β Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system. Methods. We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry. Results. The orbital properties of both planets are constrained with a semi-major axis of 9.8 ± 0.4 au and 2.7 ± 0.02 au for b and c, respectively, and eccentricities of 0.09 ± 0.1 and 0.27 ± 0.07, assuming the HIPPARCOS distance. We note that despite these low fitting error bars, the eccentricity of β Pictoris c might still be over-estimated. If no prior is provided on the mass of β Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of β Pictoris b, we find a solution in the 10–11 MJup range. Conversely, β Pictoris c’s mass is well constrained, at 7.8 ± 0.4 MJup, assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the β Pictoris system. The absolute astrometry HIPPARCOS-Gaia data are consistent with the solutions presented here at the 2σ level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5 MJup closer than 3 au, and more massive than 3.5 MJup between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1–2 MJup. Conclusions. Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of β Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of β Pictoris b.
Published: 2020
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21. Models of high-frequency quasi-periodic oscillations and black hole spin estimates in Galactic microquasars

Author: Eva Šrámková, J. Horak, Andrea Kotrlova, Debora Lančová, Kateřina Goluchová, Marek A. Abramowicz, Zdenek Stuchlik, Odele Straub, Gabriel Török, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire Univers et Théories (LUTH (UMR_8102)), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Geodesic, Astrophysics::High Energy Astrophysical Phenomena, black hole physics, Rotational symmetry, FOS: Physical sciences, Astrophysics, Approx, 01 natural sciences, X-rays: binaries, accretion, Accretion disc, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Oscillation, accretion disks, Astronomy and Astrophysics, Accretion (astrophysics), Black hole, Neutron star, Space and Planetary Science, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract: We explore the influence of non-geodesic pressure forces that are present in an accretion disk on the frequencies of its axisymmetric and non-axisymmetric epicyclic oscillation modes. {We discuss its implications for models of high-frequency quasi-periodic oscillations (QPOs) that have been observed in the X-ray flux of accreting black holes (BHs) in the three Galactic microquasars, GRS 1915+105, GRO J1655$-$40 and XTE J1550$-$564. We focus on previously considered QPO models that deal with low azimuthal number epicyclic modes, $\lvert m \rvert \leq 2$, and outline the consequences for the estimations of BH spin, $a\in[0,1]$.} For four out of six examined models, we find only small, rather insignificant changes compared to the geodesic case. For the other two models, on the other hand, there is a fair increase of the estimated upper limit on the spin. Regarding the QPO model's falsifiability, we find that one particular model from the examined set is incompatible with the data. If the microquasar's spectral spin estimates that point to $a>0.65$ were fully confirmed, two more QPO models would be ruled out. Moreover, if two very different values of the spin, such as $a\approx 0.65$ in GRO J1655$-$40 vs. $a\approx 1$ in GRS 1915+105, were confirmed, all the models except one would remain unsupported by our results. Finally, we discuss the implications for a model recently proposed in the context of neutron star (NS) QPOs as a disk-oscillation-based modification of the relativistic precession model. This model provides overall better fits of the NS data and predicts more realistic values of the NS mass compared to the relativistic precession model. We conclude that it also implies a significantly higher upper limit on the microquasar's BH spin ($a\sim 0.75$ vs. $a\sim 0.55$)., 9 pages, 6 figures, 2 tables, published in A&A, typos corrected
Published: 2020
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22. A measure of the size of the magnetospheric accretion region in TW Hydrae

Author: Pierre Kervella, Y. Clénet, M. Filho, Stefan Hippler, Wolfgang Brandner, Tom Ray, Ekkehard Wieprecht, S. Yazici, S. von Fellenberg, O. Pfuhl, M. Bauboeck, J. Sanchez-Bermudez, Andreas Eckart, C. E. Garcia Dabo, A. Ramirez, R. Fedriani, Maryam Habibi, Paulo J. V. Garcia, F. H. Vincent, M. Koutoulaki, António Amorim, Julia Stadler, T. de Zeeuw, A. Jimenez Rosales, Feng Gao, Catherine Dougados, Felix Widmann, Karine Perraut, Lucas Labadie, Myriam Benisty, R. Garcia Lopez, Reinhard Genzel, H. Bonnet, A. Buron, E. F. van Dishoeck, Silvia Scheithauer, W. J. de Wit, Jinyi Shangguan, Stefan Gillessen, T. Ott, Frank Eisenhauer, T. Paumard, Sylvestre Lacour, Pierre Léna, V. Coudé du Foresto, Matthew Horrobin, Julien Woillez, Jean-Philippe Berger, F. Haussmann, A. Natta, L. Klarmann, Z. Hubert, Odele Straub, J.-B. Le Bouquin, Johann Kolb, Erich Wiezorrek, Eckhard Sturm, Laurent Jocou, Guy Perrin, A. Caratti o Garatti, R. Grellmann, Eric Gendron, Christian Straubmeier, Th. Henning, C. Rau, Xavier Haubois, M. Wiest, Roberto Abuter, Gilles Duvert, Paola Caselli, Gérard Zins, G. Rousset, 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), School of Cosmic Physics [Dublin], and Dublin Institute for Advanced Studies (DIAS)
Subjects: Young stellar object, Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, TW Hydrae, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Multidisciplinary, 010308 nuclear & particles physics, Stellar magnetic field, Radius, Accretion (astrophysics), Stars, T Tauri star, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, [SDU]Sciences of the Universe [physics], Astrophysics::Earth and Planetary Astrophysics
Abstract: Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate the disk close to the so-called corotation radius where the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that Hydrogen is mostly emitted in a region of a few milliarcseconds across, usually located within the dust sublimation radius. Its origin is still a matter of debate and it can be interpreted as coming from the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that the Br gamma emission is spatially resolved rules out that most of the emission comes from the magnetosphere. This is due to the weak magnetic fields (some tenths of G) detected in these sources, resulting in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. However, the small angular size of the magnetosphere (a few tenths of milliarcseconds), along with the presence of winds emitting in Hydrogen make the observations interpretation challenging. Here, we present direct evidence of magnetospheric accretion by spatially resolving the inner disk of the 60 pc T Tauri star TW Hydrae through optical long baseline interferometry. We find that the hydrogen near-infrared emission comes from a region approximately 3.5 stellar radii (R*) across. This region is within the continuum dusty disk emitting region (Rcont = 7 R*) and smaller than the corotation radius which is twice as big. This indicates that the hydrogen emission originates at the accretion columns, as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (>1au)., Publish in Nature
Published: 2020
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23. Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole

Author: Wolfgang Brandner, Thomas Ott, S. von Fellenberg, Thibaut Paumard, Jason Dexter, S. Yazici, V. Lapeyrère, Reinhard Genzel, Andreas Eckart, Xavier Haubois, Gérard Zins, Karine Perraut, Odele Straub, Stefan Hippler, Christian Straubmeier, Jean-Philippe Berger, António Amorim, M. Bauböck, J.-B. Le Bouquin, Th. Henning, Yann Clénet, P. T. de Zeeuw, Idel Waisberg, Eckhard Sturm, Sylvestre Lacour, Laurent Jocou, H. Bonnet, Jinyi Shangguan, Linda J. Tacconi, Silvia Scheithauer, Eric Gendron, Guy Perrin, M. Nowak, Maryam Habibi, Ekkehard Wieprecht, Felix Widmann, Andreas Kaufer, Julien Woillez, Matthew Horrobin, N. M. Förster Schreiber, Erich Wiezorrek, Frank Eisenhauer, Pierre Léna, Paulo J. V. Garcia, A. Jiménez-Rosales, G. Rodríguez-Coira, F. Vincent, Pierre Kervella, Oliver Pfuhl, Feng Gao, Vitor Cardoso, Lieselotte Jochum, Julia Stadler, Stefan Gillessen, Roberto Abuter, Observatoire de Paris, Université Paris sciences et lettres (PSL), 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), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), GRAVITY, and 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)
Subjects: Astrophysics and Astronomy, gr-qc, astro-ph.GA, black hole physics, Highly elliptical orbit, FOS: Physical sciences, Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, General Relativity and Quantum Cosmology, symbols.namesake, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, relativistic processes, Physics, Galaxy: nucleus, 010308 nuclear & particles physics, General Relativity and Cosmology, Astronomy and Astrophysics, Orbital period, Astrophysics - Astrophysics of Galaxies, Black hole, Radial velocity, Orbit, Space and Planetary Science, gravitation, [SDU]Sciences of the Universe [physics], Kepler orbit, Astrophysics of Galaxies (astro-ph.GA), [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Precession, symbols, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Instrumentation and Methods for Astrophysics, Schwarzschild radius, astro-ph.IM
Abstract: The star S2 orbiting the compact radio source Sgr A* is a precision probe of the gravitational field around the closest massive black hole (candidate). Over the last 2.7 decades we have monitored the star's radial velocity and motion on the sky, mainly with the SINFONI and NACO adaptive optics (AO) instruments on the ESO VLT, and since 2017, with the four-telescope interferometric beam combiner instrument GRAVITY. In this paper we report the first detection of the General Relativity (GR) Schwarzschild Precession (SP) in S2's orbit. Owing to its highly elliptical orbit (e = 0.88), S2's SP is mainly a kink between the pre-and post-pericentre directions of motion ~ +- 1 year around pericentre passage, relative to the corresponding Kepler orbit. The superb 2017-2019 astrometry of GRAVITY defines the pericentre passage and outgoing direction. The incoming direction is anchored by 118 NACO-AO measurements of S2's position in the infrared reference frame, with an additional 75 direct measurements of the S2-Sgr A* separation during bright states ('flares') of Sgr A*. Our 14-parameter model fits for the distance, central mass, the position and motion of the reference frame of the AO astrometry relative to the mass, the six parameters of the orbit, as well as a dimensionless parameter f_SP for the SP (f_SP = 0 for Newton and 1 for GR). From data up to the end of 2019 we robustly detect the SP of S2, del phi = 12' per orbital period. From posterior fitting and MCMC Bayesian analysis with different weighting schemes and bootstrapping we find f_SP = 1.10 +- 0.19. The S2 data are fully consistent with GR. Any extended mass inside S2's orbit cannot exceed ~ 0.1% of the central mass. Any compact third mass inside the central arcsecond must be less than about 1000 M_sun., accepted to A&A
Published: 2020
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24. A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating

Author: Maryam Habibi, T. Ott, Jason Dexter, Frank Eisenhauer, M. Bauböck, A. Jiménez-Rosales, Odele Straub, Feng Gao, Stefan Gillessen, Reinhard Genzel, Julia Stadler, S. von Fellenberg, S M Ressler, Felix Widmann, Alexander Tchekhovskoy, and P. T. de Zeeuw
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spectral line, symbols.namesake, 0103 physical sciences, Faraday effect, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Linear polarization, Astronomy and Astrophysics, Polarization (waves), Astrophysics - Astrophysics of Galaxies, Accretion (astrophysics), Wavelength, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), symbols, Magnetohydrodynamics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Galactic center black hole candidate Sgr A* is the best target for studies of low-luminosity accretion physics, including with near-infrared and submillimeter wavelength long baseline interferometry experiments. Here we compare images and spectra generated from a parameter survey of general relativistic MHD simulations to a set of radio to near-infrared observations of Sgr A*. Our models span the limits of weak and strong magnetization and use a range of sub-grid prescriptions for electron heating. We find two classes of scenarios can explain the broad shape of the submillimeter spectral peak and the highly variable near-infrared flaring emission. Weakly magnetized "disk-jet" models where most of the emission is produced near the jet wall, consistent with past work, as well as strongly magnetized (magnetically arrested disk) models where hot electrons are present everywhere. Disk-jet models are strongly depolarized at submillimeter wavelengths as a result of strong Faraday rotation, inconsistent with observations of Sgr A*. We instead favor the strongly magnetized models, which provide a good description of the median and highly variable linear polarization signal. The same models can also explain the observed mean Faraday rotation measure and potentially the polarization signals seen recently in Sgr A* near-infrared flares., 20 pages, 17 figures, MNRAS in press
Published: 2020

25. The GRAVITY young stellar object survey. II. First spatially resolved observations of the CO bandhead emission in a high-mass YSO

Author: E. F. van Dishoeck, Feng Gao, Lucas Labadie, Wing-Fai Thi, Catherine Dougados, R. Fedriani, Paulo J. V. Garcia, Stefan Gillessen, Matthew Horrobin, Christian Straubmeier, J. Sanchez-Bermudez, Frederic H. Vincent, L. Klarmann, Th. Henning, Gérard Rousset, Eckhard Sturm, Laurent Jocou, Andreas Eckart, Thibaut Paumard, R. Grellmann, A. Caratti o Garatti, Arjan Bik, T. Ott, Odele Straub, Bernard Lazareff, V. Coudé du Foresto, Frank Eisenhauer, H. Linz, J.-B. Le Bouquin, Eric Gendron, António Amorim, Tom Ray, Jean-Phillipe Berger, Pierre Léna, Paola Caselli, Silvia Scheithauer, Sylvestre Lacour, Felix Widmann, Paulo Gordo, Gilles Duvert, R. Garcia Lopez, Reinhard Genzel, Guy Perrin, J. Stadler, Pierre Kervella, Karine Perraut, M. Koutoulaki, Myriam Benisty, Wolfgang Brandner, Yann Clénet, P. T. de Zeeuw, Jinyi Shangguan, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: stars, 010504 meteorology & atmospheric sciences, Stellar mass, Gaussian, Young stellar object, Overtone, FOS: Physical sciences, Astrophysics, 01 natural sciences, symbols.namesake, formation -stars, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, observational, massive -infrared, 010303 astronomy & astrophysics, infrared: stars, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, [PHYS]Physics [physics], stars: formation, Astronomy and Astrophysics, Position angle, Ellipsoid, Astrophysics - Astrophysics of Galaxies, stars: massive, Interferometry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, techniques: interferometric, interferometric -techniques, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), Closure phase, symbols, Astrophysics::Earth and Planetary Astrophysics, methods: observational, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], techniques: spectroscopic, stars -techniques, spectroscopicmethods
Abstract: The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. We deploy near-infrared (NIR) spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3-2.4 $\mu$m). We present the first GRAVITY/VLTI observations at high spectral (R=4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS2. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases ($\leq$8$^{\circ}$). Our best ellipsoid model provides a disc inclination of 34$^{\circ}$$\pm$1$^{\circ}$, a disc major axis position angle of 166$^{\circ}$$\pm$1$^{\circ}$, and a disc diameter of 3.99$\pm$0.09 mas (or 1.69$\pm$0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74$\pm^{0.08}_{0.07}$ mas (1.16$\pm$0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and $PA$ matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of $M_*\sim$14.7$^{+2}_{-3.6}$ M$_{\odot}$ by combining our interferometric and spectral modelling results., Comment: Accepted for publication in A&A letters
Published: 2020
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26. The GRAVITY young stellar object survey

Author: Paola Caselli, E. F. van Dishoeck, Feng Gao, Jaime E. Pineda, Karine Perraut, Lucas Labadie, Stefan Gillessen, Catherine Dougados, Felix Widmann, E. Sturm, Odele Straub, Eric Gendron, J.-B. Le Bouquin, Christian Straubmeier, L. Klarmann, Mercedes E. Filho, A. Eckart, Thomas Ott, J. Sanchez-Bermudez, Th. Henning, A. Drescher, V. Lapeyrère, Gérard Rousset, Zoltan Hubert, Matthew Horrobin, Paulo J. V. Garcia, Gilles Duvert, Julien Woillez, G. Heissel, Thibaut Paumard, Jean-Phillipe Berger, G. Rodríguez-Coira, R. Grellmann, Frederic H. Vincent, Laurent Jocou, J. Stadler, S. D. von Fellenberg, Sylvestre Lacour, António Amorim, Guy Perrin, Pierre Kervella, V. Coudé du Foresto, Frank Eisenhauer, R. Garcia Lopez, Reinhard Genzel, Dominique Segura-Cox, Pierre Léna, M. Bauböck, Myriam Benisty, T. Taro Shimizu, A. Caratti o Garatti, A. Jiménez-Rosales, Yann Clénet, P. T. de Zeeuw, Wolfgang Brandner, and Jinyi Shangguan
Subjects: Young stellar object, FOS: Physical sciences, Context (language use), Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Angular resolution, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Very Large Telescope, 010308 nuclear & particles physics, Astronomy and Astrophysics, Accretion (astrophysics), Vortex, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Protoplanetary disks drive some of the formation process (e.g., accretion, gas dissipation, formation of structures, etc.) of stars and planets. Understanding such physical processes is one of the main astrophysical questions. HD 163296 is an interesting young stellar object for which infrared and sub-millimeter observations have shown a prominent circumstellar disk with gaps plausibly created by forming planets. This study aims at characterizing the morphology of the inner disk in HD 163296 with multi-epoch near-infrared interferometric observations performed with GRAVITY at the Very Large Telescope Interferometer (VLTI). Our goal is to depict the K-band (lambda_0 ~ 2.2 um) structure of the inner rim with milliarcsecond (sub-au) angular resolution. Our data is complemented with archival PIONIER (H-band; lambda_0 ~ 1.65 um) data of the source. We performed a Gradient Descent parametric model fitting to recover the sub-au morphology of our source. Our analysis shows the existence of an asymmetry in the disk surrounding the central star of HD 163296. We confirm variability of the disk structure in the inner ~2 mas (0.2 au). While variability of the inner disk structure in this source has been suggested by previous interferometric studies, this is the first time that it is confirmed in the H- and K-bands by using a complete analysis of the closure phases and squared visibilities over several epochs. Because of the separation from the star, position changes, and persistence of this asymmetric structure on timescales of several years, we argue that it is a dusty feature (e.g., a vortex or dust clouds), probably, made by a mixing of sillicate and carbon dust and/or refractory grains, inhomogeneously distributed above the mid-plane of the disk., Accepted to be published in Astronomy and Astrophysics; main-body: 11 pages, 3 figures and 3 tables
Published: 2021
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27. Peering into the formation history of β Pictoris b with VLTI/GRAVITY long-baseline interferometry

Author: Gérard Rousset, N. M. Förster Schreiber, E. F. van Dishoeck, Laurent Pueyo, Frank Eisenhauer, Pierre Léna, H. Bonnet, Jingxiu Wang, Eric Gendron, Stefan Gillessen, Anne-Lise Maire, Yann Clénet, P. T. de Zeeuw, Hervé Beust, Jinyi Shangguan, S. Yazici, Julien Woillez, Thibaut Paumard, Claudia Paladini, C. Collin, M. Nowak, Sylvestre Lacour, Thomas Ott, D. Ziegler, F. Chapron, António Amorim, Erich Wiezorrek, Oliver Pfuhl, Feng Gao, A. Buron, P. Fédou, Z. Hubert, R. Garcia Lopez, Reinhard Genzel, Wolfgang Brandner, Odele Straub, J.-B. Le Bouquin, Ekkehard Wieprecht, Jean-Phillipe Berger, Stefan Hippler, Benjamin Charnay, Eckhard Sturm, F. Vincent, Pierre Kervella, Faustine Cantalloube, Laurent Jocou, G. Rodríguez-Coira, Sebastian Rabien, Roberto Abuter, Anne-Marie Lagrange, Mickael Bonnefoy, C. Rau, Linda J. Tacconi, Guy Perrin, Andreas Eckart, Silvia Scheithauer, Felix Widmann, Karine Perraut, V. Lapeyrère, P. Mollière, Gilles Duvert, Christian Straubmeier, F. Haußmann, Th. Henning, Jason Dexter, V. Coudé du Foresto, R. Dembet, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Planetesimal, 010504 meteorology & atmospheric sciences, planets and satellites, formation -planets and satellites, atmospheres -techniques, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, β Pictoris, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, individual, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Orbital elements, Physics, [PHYS]Physics [physics], Earth and Planetary Astrophysics (astro-ph.EP), Very Large Telescope, Giant planet, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Astrometry, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics::Earth and Planetary Astrophysics, interferometricstars, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Instrumentation and Methods for Astrophysics, Planetary mass, Astrophysics - Earth and Planetary Astrophysics
Abstract: Our objective is to estimate the C/O ratio in the atmosphere of beta Pictoris b and obtain an estimate of the dynamical mass of the planet, as well as to refine its orbital parameters using high-precision astrometry. We used the GRAVITY instrument with the four 8.2 m telescopes of the Very Large Telescope Interferometer to obtain K-band spectro-interferometric data on $\beta$ Pic b. We extracted a medium resolution (R=500) K-band spectrum of the planet and a high-precision astrometric position. We estimated the planetary C/O ratio using two different approaches (forward modeling and free retrieval) from two different codes (ExoREM and petitRADTRANS, respectively). Finally, we used a simplified model of two formation scenarios (gravitational collapse and core-accretion) to determine which can best explain the measured C/O ratio. Our new astrometry disfavors a circular orbit for $\beta$ Pic b ($e=0.15^{+0.05}_{-0.04}$). Combined with previous results and with Hipparcos/GAIA measurements, this astrometry points to a planet mass of $M = 12.7\pm{}2.2\,M_\mathrm{Jup}$. This value is compatible with the mass derived with the free-retrieval code petitRADTRANS using spectral data only. The forward modeling and free-retrieval approches yield very similar results regarding the atmosphere of beta Pic b. In particular, the C/O ratios derived with the two codes are identical ($0.43\pm{}0.05$ vs $0.43^{+0.04}_{-0.03}$). We argue that if the stellar C/O in $\beta$ Pic is Solar, then this combination of a very high mass and a low C/O ratio for the planet suggests a formation through core-accretion, with strong planetesimal enrichment., Comment: 14 pages + 7 page appendix, 7 figures, accepted for pulication
Published: 2020
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28. A Galactic centre gravitational-wave Messenger

Author: Odele Straub, Marek A. Abramowicz, M. Bejger, Eric Gourgoulhon, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), 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), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), 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: Milky Way, Astrophysics::High Energy Astrophysical Phenomena, lcsh:Medicine, FOS: Physical sciences, Orbital decay, 01 natural sciences, Article, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], 010306 general physics, lcsh:Science, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Supermassive black hole, Multidisciplinary, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Gravitational wave, lcsh:R, Astronomy, General relativity and gravity, Galaxy, Orbit, Sagittarius A, Orbital motion, lcsh:Q, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Compact astrophysical objects, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Our existence in the Universe resulted from a rare combination of circumstances. The same must hold for any highly developed extraterrestrial civilisation, and if they have ever existed in the Milky Way, they would likely be scattered over large distances in space and time. However, all technologically advanced species must be aware of the unique property of the galactic centre: it hosts Sagittarius A* (Sgr A*), the closest supermassive black hole to anyone in the Galaxy. A civilisation with sufficient technical know-how may have placed material in orbit around Sgr A* for research, energy extraction, and communication purposes. In either case, its orbital motion will necessarily be a source of gravitational waves. We show that a Jupiter-mass probe on the retrograde innermost stable circular orbit around Sgr A* emits, depending on the black hole spin, at a frequency of $f_{GW} = 0.63 - 1.07$ mHz and with a power of $P_{GW}=2.7 \times\, 10^{36} - 2.0 \times\, 10^{37}$ erg/s. We discuss that the energy output of a single star is sufficient to stabilise the location of an orbiting probe for a billion years against gravitational wave induced orbital decay. Placing and sustaining a device near Sgr A* is therefore astrophysically possible. Such a probe will emit an unambiguously artificial continuous gravitational wave signal that is observable with LISA-type detectors., Comment: 7 pages, 2 figures, published in Scientific Reports
Published: 2020
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29. The GRAVITY Young Stellar Object survey I. Probing the disks of Herbig Ae/Be stars in terrestrial orbits

Author: S. Yazici, Oliver Pfuhl, Thomas Henning, J. Bouvier, Stefan Hippler, V. Coudé du Foresto, Thomas Ott, J. Sanchez-Bermudez, Lucas Labadie, E. F. van Dishoeck, Myriam Benisty, Sebastian Rabien, Stefan Gillessen, Frank Eisenhauer, Frederic H. Vincent, A. Caratti o Garatti, Karine Perraut, Chien-Cheng Lin, Laurent Jocou, Andreas Eckart, Jaime E. Pineda, Matthew Horrobin, Christian Straubmeier, Roberto Abuter, Idel Waisberg, Feng Gao, L. Klarmann, Catherine Dougados, Imke Wank, Antoine Mérand, C. Rau, Gérard Rousset, Felix Widmann, Sarah Kendrew, Guy Perrin, A. Buron, P. T. de Zeeuw, Thomas P. Ray, R. Grellmann, Wolfgang Brandner, António Amorim, Bernard Lazareff, Dominique Segura-Cox, Paulo Gordo, Erich Wiezorrek, Henri Bonnet, F. Eupen, Eric Gendron, F. Haussmann, M. Koutoulaki, Yann Clénet, Silvia Scheithauer, Xavier Haubois, Paola Caselli, M. Wiest, Paulo J. V. Garcia, Gilles Duvert, Reinhard Genzel, Julien Woillez, Thibaut Paumard, E. Sturm, Jason Dexter, Jean-Philippe Berger, Z. Hubert, Sylvestre Lacour, Odele Straub, J.-B. Le Bouquin, Pierre Léna, R. Garcia-Lopez, Ekkehard Wieprecht, Pierre Kervella, Faustine Cantalloube, 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]), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: stars, Young stellar object, Population, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, Thermal, Astrophysics::Solar and Stellar Astrophysics, high angular resolutiontechniques, education, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Earth and Planetary Astrophysics (astro-ph.EP), education.field_of_study, Very Large Telescope, 010308 nuclear & particles physics, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), formation -circumstellar matter -infrared, interferometric, Closure phase, Terrestrial planet, Astrophysics::Earth and Planetary Astrophysics, ISM -techniques, Astrophysics - Earth and Planetary Astrophysics
Abstract: The formation and the evolution of protoplanetary disks are important stages in the lifetime of stars. The processes of disk evolution and planet formation are intrinsically linked. We spatially resolve with GRAVITY/VLTI in the K-band the sub au-scale region of 27 stars to gain statistical understanding of their properties. We look for correlations with stellar parameters, such as luminosity, mass, temperature and age. Our sample also cover a range of various properties in terms of reprocessed flux, flared or flat morphology, and gaps. We developed semi-physical geometrical models to fit our interferometric data. Our best models correspond to smooth and wide rings, implying that wedge-shaped rims at the dust sublimation edge are favored, as found in the H-band. The closure phases are generally non-null with a median value of ~10 deg, indicating spatial asymmetries of the intensity distributions. Multi-size grain populations could explain the closure phase ranges below 20-25 deg but other scenarios should be invoked to explain the largest ones. Our measurements extend the Radius-Luminosity relation to ~1e4 Lsun and confirm the significant spread around the mean relation observed in the H-band. Gapped sources exhibit a large N-to-K band size ratio and large values of this ratio are only observed for the members of our sample that would be older than 1 Ma, less massive, and with lower luminosity. In the 2 Ms mass range, we observe a correlation in the increase of the relative age with the transition from group II to group I, and an increase of the N-to-K size ratio. However, the size of the current sample does not yet permit us to invoke a clear universal evolution mechanism across the HAeBe mass range. The measured locations of the K-band emission suggest that these disks might be structured by forming young planets, rather than by depletion due to EUV, FUV, and X-ray photo-evaporation., Comment: Accepted for publication in A&A; 23 pages, 16 figures, 7 tables
Published: 2019
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30. Accretion discs.

Author: Marek Abramowicz and Odele Straub
Published: 2014
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31. A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty

Author: Idel Waisberg, Thibaut Paumard, Julien Woillez, Jason Dexter, Oliver Pfuhl, Stefan Gillessen, Thomas Henning, Senol Yazici, Matthew Horrobin, Stefan Hippler, Christian Straubmeier, Karine Perraut, Odele Straub, J.-B. Le Bouquin, Sebastian Rabien, Amiel Sternberg, F. Vincent, António Amorim, Laurent Jocou, Vincent Lapeyrere, Reinhard Genzel, V. Coudé du Foresto, Feng Gao, Xavier Haubois, Gilles Duvert, Ekkehard Wieprecht, Jean-Philippe Berger, Paulo J. V. Garcia, Maryam Habibi, Thomas Ott, A. Jiménez-Rosales, Ortwin Gerhard, S. von Fellenberg, Linda J. Tacconi, G. Rousset, Eric Gendron, Guy Perrin, Pierre Kervella, Frank Eisenhauer, G. Rodriguez Coira, R. Abuter, Felix Widmann, Pierre Léna, Eckhard Sturm, Silvia Scheithauer, N. M. Förster Schreiber, Erich Wiezorrek, Henri Bonnet, Andreas Eckart, M. Bauböck, Sylvestre Lacour, Yann Clénet, P. T. de Zeeuw, Wolfgang Brandner, 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 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 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 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)
Subjects: Physics, Galaxy: nucleus, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Galactic Center, black hole physics, FOS: Physical sciences, Astronomy and Astrophysics, Orbital eccentricity, Astrometry, Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Redshift, Black hole, Orbit, Interferometry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, astrometry, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Gravitational redshift
Abstract: We present a 0.16% precise and 0.27% accurate determination of R0, the distance to the Galactic Center. Our measurement uses the star S2 on its 16-year orbit around the massive black hole Sgr A* that we followed astrometrically and spectroscopically for 27 years. Since 2017, we added near-infrared interferometry with the VLTI beam combiner GRAVITY, yielding a direct measurement of the separation vector between S2 and Sgr A* with an accuracy as good as 20 micro-arcsec in the best cases. S2 passed the pericenter of its highly eccentric orbit in May 2018, and we followed the passage with dense sampling throughout the year. Together with our spectroscopy, in the best cases with an error of 7 km/s, this yields a geometric distance estimate: R0 = 8178 +- 13(stat.) +- 22(sys.) pc. This work updates our previous publication in which we reported the first detection of the gravitational redshift in the S2 data. The redshift term is now detected with a significance level of 20 sigma with f_redshift = 1.04 +- 0.05., Comment: 9 pages, 7 figures, submitted to A&A
Published: 2019
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32. Scalar field effects on the orbit of S2 star

Author: Andreas Eckart, A. Jiménez-Rosales, Thibaut Paumard, Odele Straub, J.-B. Le Bouquin, V. Coudé Du Forest, Eckhard Sturm, Feng Gao, Maryam Habibi, Pierre Kervella, T. de Zeeuw, G. Rodriguez Coira, Jason Dexter, Laurent Jocou, Idel Waisberg, Myriam Benisty, Oliver Pfuhl, T. Ott, Christian Straubmeier, António Amorim, Paulo Gordo, Frank Eisenhauer, S. von Fellenberg, Pierre Léna, M. Bauböck, M. Pössel, Gilles Duvert, Sylvestre Lacour, Stefan Gillessen, Jean-Philippe Berger, R. Genzel, Yann Clénet, G. Rousset, F. Vincent, Paulo J. V. Garcia, Karine Perraut, Guy Perrin, Felix Widmann, M. Ferreira, Eric Gendron, Matthew Horrobin, 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 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), GRAVITY, 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), and 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)
Subjects: Field (physics), Dark matter, black hole physics, FOS: Physical sciences, torus, General Relativity and Quantum Cosmology (gr-qc), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Compact star, mass: scalar, 01 natural sciences, General Relativity and Quantum Cosmology, dark matter, Gravitation, precession, black hole: Kerr, energy: rotation, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, central region, Astronomy and Astrophysics, hair, star: orbit, celestial mechanics, Astrophysics - Astrophysics of Galaxies, mass: coupling, Galaxy: centre, Galaxy, field theory: scalar, Black hole, Rotating black hole, 13. Climate action, Space and Planetary Science, gravitation, Astrophysics of Galaxies (astro-ph.GA), [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], galaxy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Scalar field, superradiance, signature
Abstract: Precise measurements of the S-stars orbiting SgrA* have set strong constraints on the nature of the compact object at the centre of the Milky Way. The presence of a black hole in that region is well established, but its neighboring environment is still an open debate. In that respect, the existence of dark matter in that central region may be detectable due to its strong signatures on the orbits of stars: the main effect is a Newtonian precession which will affect the overall pericentre shift of S2, the latter being a target measurement of the GRAVITY instrument. The exact nature of this dark matter (e.g., stellar dark remnants or diffuse dark matter) is unknown. This article assumes it to be an scalar field of toroidal distribution, associated with ultra-light dark matter particles, surrounding the Kerr black hole. Such a field is a form of "hair" expected in the context of superradiance, a mechanism that extracts rotational energy from the black hole. Orbital signatures for the S2 star are computed and shown to be detectable by GRAVITY. The scalar field can be constrained because the variation of orbital elements depends both on the relative mass of the scalar field to the black hole and on the field mass coupling parameter., Comment: 17 pages, 6 figures. v2: added some references and fixed minor typos to match version in press in MNRAS
Published: 2019
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33. Multi-wavelength torus–jet model for Sagittarius A

Author: Thibaut Paumard, A. A. Zdziarski, Maciek Wielgus, Odele Straub, Frederic H. Vincent, Marek A. Abramowicz, Guy Perrin, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-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: Physics, Sagittarius A, Event Horizon Telescope, Spectral index, Galaxy: center, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, accretion disks, black hole physics, Astronomy and Astrophysics, Context (language use), Torus, Astrophysics, 01 natural sciences, Galaxy, Black hole, accretion, Space and Planetary Science, 0103 physical sciences, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Schwarzschild radius, Astrophysics::Galaxy Astrophysics, relativistic processes
Abstract: Context. The properties of the accretion/ejection flow surrounding the supermassive central black hole of the Galaxy Sgr A* will be scrutinized by the new-generation instrument GRAVITY and the Event Horizon Telescope (EHT). Developing fast, robust, and simple models of such flows is therefore important and very timely. Aims. We want to model the quiescent emission of Sgr A* from radio to mid-infrared wavelengths, using thermal and nonthermal synchrotron. The radiation is emitted by the overlay of a magnetized compact torus close to the black hole, and a large-scale magnetized jet. We compare model spectra and images to the multi-wavelength observable constraints available to date. We simulate EHT observations at 1.3 mm of the best-fit model for different inclinations. methods. We use a simple analytic description for the geometry of the torus and jet. We model their emission by thermal synchrotron and κ-distribution synchrotron, respectively. We use relativistic ray tracing to compute simulated spectra and images, restricting our analysis to the Schwarzschild (zero spin) case. A best-fit is found by adjusting the simulated spectra to the latest observed data, and we check the consistency of our spectral best fits with the radio-image sizes and infrared spectral index constraints. We use the open-source eht-imaging library to generate EHT-reconstructed images. Results. We find perfect spectral fit ( χred2 ≈ 1) both for nearly face-on and nearly edge-on views. These best fits give parameter values very close to those found by the most recent numerical simulations, which are much more complex than our model. The intrinsic radio size of Sgr A* is found to be in reasonable agreement with the centimetric observed constraints. Our best-fit infrared spectral index is in perfect agreement with the latest constraints. Our emission region at 1.3 mm, although larger than the early-EHT Gaussian best fit, does contain bright features at the ≲40 μas scale. EHT-reconstructed images show that torus/jet-specific features persist after the reconstruction procedure, and that these features are sensitive to inclination. Conclusions. The main interest of our model is to provide a simple and fast model of the quiescent state of Sgr A*, which gives extremely similar results to those of state-of-the-art numerical simulations. Our model is easy to use and we publish all the material necessary to reproduce our spectra and images, meaning that anyone interested can use our results relatively straightforwardly. We hope that such a public tool will be useful in the context of the recent and near-future GRAVITY and EHT results.
Published: 2019
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34. Timescale of twin-peak quasi-periodic oscillations and mass of accreting neutron stars

Author: Kateřina Goluchová, Eva Šrámková, Gabriel Török, Martin Urbanec, and Odele Straub
Subjects: Physics, High Energy Astrophysical Phenomena (astro-ph.HE), General relativity, Astrophysics::High Energy Astrophysical Phenomena, Binary number, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Accretion (astrophysics), Magnetic field, Neutron star, Pulsar, Space and Planetary Science, Millisecond pulsar, Orbital motion, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Einstein's general relativity predicts that orbital motion of accreted gas approaching a neutron star (NS) in a NS low-mass X-ray binary (LMXB) system occurs on a time scale proportional to the NS mass. Radiation of the gas accounts for most of the observed LMXBs variability. In more than a dozen of sources twin-peak quasi-periodic oscillations (QPOs) have been observed. Inspired by the expected proportionality between periods of orbital motion and NS mass we present a straightforward comparison among these sources. We investigate relations between QPO periods and their ratios and identify characteristic time scales of QPOs associated to individual sources. These timescales are likely determined by the relative mass of each NS. We show that the characteristic time scale of the millisecond pulsar XTE J1807.4-294 is longer than for most other NS LMXBs. Consequently, models of QPOs that consider geodesic orbital frequencies imply that the X-ray pulsars' mass has to be about 50 % higher than the average mass of other sources. Consideration of other X-ray pulsars indicates that the exceptionality of XTE J1807.4-294 cannot be related to NS magnetic field in any simple manner. We suggest that QPOs observed in this source can help to discriminate between the proposed versions of the NS equation of state., Comment: 9 pages, 6 figures, 1 table, accepted for publication in MNRAS
Published: 2019
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35. Test of the Einstein Equivalence Principle near the Galactic Center Supermassive Black Hole

Author: N. M. Förster Schreiber, Karine Perraut, Ekkehard Wieprecht, Christian Straubmeier, Stefan Hippler, Th. Henning, Thibaut Paumard, Frank Eisenhauer, Felix Widmann, Pierre Kervella, Laurent Jocou, Paulo J. V. Garcia, Pierre Léna, Silvia Scheithauer, Matthew Horrobin, M. Bauböck, Thomas Ott, Maryam Habibi, Oliver Pfuhl, Jason Dexter, Linda J. Tacconi, S. von Fellenberg, A. Jimenez Rosales, Yann Clénet, P. T. de Zeeuw, Sylvestre Lacour, Gilles Duvert, Andreas Eckart, Guy Perrin, Amiel Sternberg, Senol Yazici, Eckhard Sturm, Erich Wiezorrek, Eric Gendron, Idel Waisberg, M. Ebert, Reinhard Genzel, F. Vincent, António Amorim, Sebastian Rabien, G. Rodríguez-Coira, Z. Hubert, Xavier Haubois, Vincent Lapeyrere, Odele Straub, J.-B. Le Bouquin, Wolfgang Brandner, G. Rousset, Feng Gao, V. Coudé du Foresto, Jean-Philippe Berger, Stefan Gillessen, 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), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GRAVITY, 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 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: General Physics and Astronomy, FOS: Physical sciences, Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Gravitation and Astrophysics, 7. Clean energy, 01 natural sciences, General Relativity and Quantum Cosmology, Gravitational potential, 0103 physical sciences, Equivalence principle, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, Supermassive black hole, Galactic Center, White dwarf, Astrophysics - Astrophysics of Galaxies, Redshift, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Black hole, Sagittarius A, Astrophysics of Galaxies (astro-ph.GA), Physics::Space Physics, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: During its orbit around the four million solar mass black hole Sagittarius A* the star S2 experiences significant changes in gravitational potential. We use this change of potential to test one part of the Einstein equivalence principle: the local position invariance (LPI). We study the dependency of different atomic transitions on the gravitational potential to give an upper limit on violations of the LPI. This is done by separately measuring the redshift from hydrogen and helium absorption lines in the stellar spectrum during its closest approach to the black hole. For this measurement we use radial velocity data from 2015 to 2018 and combine it with the gravitational potential at the position of S2, which is calculated from the precisely known orbit of S2 around the black hole. This results in a limit on a violation of the LPI of $|\beta_{He}-\beta_{H}| = (2.4 \pm 5.1) \cdot 10^{-2}$. The variation in potential that we probe with this measurement is six magnitudes larger than possible for measurements on Earth, and a factor ten larger than in experiments using white dwarfs. We are therefore testing the LPI in a regime where it has not been tested before., Comment: Accepted for publication in Physical Review Letters
Published: 2019
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36. SAGE: finding IMBH in the black hole desert

Author: Odele Straub, Lester David, F. H. Vincent, V. Lapeyrere, Aglae Kellerer, Julien Woillez, Karan Jani, Pierre Bourget, A. Le Tiec, J-Y. Vinet, M. Nowak, O. Godet, Sylvestre Lacour, J. Martino, AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), 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), Laboratoire Univers et Théories (LUTH (UMR_8102)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Relativiste Théories Expériences Métrologie Instrumentation Signaux (ARTEMIS), 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), 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), 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), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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), 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 de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), 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), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Nice Sophia Antipolis (1965 - 2019) (UNS), 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), and 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)
Subjects: coalescence, Physics and Astronomy (miscellaneous), Astrophysics::High Energy Astrophysical Phenomena, interferometer, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), triangulation, 01 natural sciences, 7. Clean energy, General Relativity and Quantum Cosmology, Observatory, 0103 physical sciences, 010306 general physics, effect: solar, orbit, Physics, Solar mass, Supermassive black hole, LISA, mass: solar, 010308 nuclear & particles physics, Gravitational wave, beam: width, Geosynchronous orbit, gravitational radiation, Astronomy, black hole: mass, Mass ratio, optics, recombination, laser, Black hole, observatory, detector: sensitivity, Interferometry, 13. Climate action, trajectory, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], mass ratio
Abstract: SAGE (SagnAc interferometer for Gravitational wavE) is a project for a space observatory based on multiple 12-U CubeSats in geosynchronous orbit. The objective is a fast track mission which would fill the observational gap between LISA and ground based observatories. With albeit a lower sensitivity, it would allow early investigation of the nature and event rate of intermediate-mass black hole (IMBH) mergers, constraining our understanding of the universe formation by probing the building up of IMBH up to supermassive black holes. Technically, the CubeSats would create a triangular Sagnac interferometer with 140.000km roundtrip arm length, optimized to be sensitive to gravitational waves at frequencies between 10mHz and 2Hz. The nature of the Sagnac measurement makes it almost insensitive to position error, enabling the use of spacecrafts in ballistic trajectories. The light source and recombination units of the interferometer are based on compact fibered technologies without bulk optics. A peak sensitivity of 23 pm/sqrt(Hz) is expected at 1Hz assuming a 200mW internal laser source and 10-centimeter diameter apertures. Because of the absence of a test mass, the main limitation would come from the non-gravitational forces applied on the spacecrafts. However, conditionally upon our ability to partially post-process the effect of solar wind and solar pressure, SAGE would allow detection of gravitational waves with strains as low as a few 1e-19 within the 0.1 to 1Hz range. Averaged over the entire sky, and including the antenna gain of the Sagnac interferometer, the SAGE observatory would sense equal mass black hole mergers in the 1e4 to 1e6 solar masses range up to a luminosity distance of 800Mpc. Additionally, coalescence of stellar black holes (10Msun) around SMBH (IMBH) forming extreme (intermediate) mass ratio inspirals could be detected within a sphere of radius 200Mpc., Comment: Accepted in Class. Quantum Grav
Published: 2019
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37. An image of the dust sublimation region in the nucleus of NGC 1068

Author: Sebastian F. Hönig, António Amorim, Idel Waisberg, N. M. Förster Schreiber, Feng Gao, Wolfgang Brandner, Paulo J. V. Garcia, T. Taro Shimizu, Linda J. Tacconi, Amiel Sternberg, D. Gratadour, Guy Perrin, Konrad R. W. Tristram, Jason Dexter, Felix Widmann, Andreas Eckart, Mercedes Prieto, P.-O. Petrucci, Bradley M. Peterson, Karine Perraut, Oliver Pfuhl, Sylvestre Lacour, Eckhard Sturm, Frank Eisenhauer, Julien Woillez, Stefan Gillessen, Ric Davies, Jinyi Shangguan, Odele Straub, Dieter Lutz, Makoto Kishimoto, Yann Clénet, P. T. de Zeeuw, Hagai Netzer, P. Vermot, Thibaut Paumard, Thomas Ott, Florentin Millour, Daniel Rouan, Marc Schartmann, Reinhard Genzel, Christian Straubmeier, Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, 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 ), and 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)
Subjects: 010504 meteorology & atmospheric sciences, galaxies: active, FOS: Physical sciences, Astrophysics, 01 natural sciences, Observatory, 0103 physical sciences, medicine, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Physics, Very Large Telescope, Astronomy and Astrophysics, Position angle, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies: Seyfert, Interferometry, medicine.anatomical_structure, Space and Planetary Science, techniques: interferometric, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), Sublimation (phase transition), galaxies: nuclei, Nucleus
Abstract: We present near-infrared interferometric data on the Seyfert 2 galaxy NGC 1068, obtained with the GRAVITY instrument on the European Southern Observatory Very Large Telescope Interferometer. The extensive baseline coverage from 5 to 60 M\lambda allowed us to reconstruct a continuum image of the nucleus with an unrivaled 0.2 pc resolution in the K-band. We find a thin ring-like structure of emission with a radius r = 0.24+/-0.03 pc, inclination i = 70+/-5 deg, position angle PA = -50+/-4 deg, and h/r < 0.14, which we associate with the dust sublimation region. The observed morphology is inconsistent with the expected signatures of a geometrically and optically thick torus. Instead, the infrared emission shows a striking resemblance to the 22 GHz maser disc, which suggests they share a common region of origin. The near-infrared spectral energy distribution indicates a bolometric luminosity of (0.4-4.7) x 10^45 erg/s, behind a large A_K ~ 5.5 (A_V ~ 90) screen of extinction that also appears to contribute significantly to obscuring the broad line region., Comment: Accepted for publication in Astronomy and Astrophysics. 13 pages with 7 figures
Published: 2019
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38. Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*

Author: Linda J. Tacconi, Eckhard Sturm, Laurent Jocou, Julien Woillez, Guy Perrin, Bernard Lazareff, Christian Straubmeier, P. M. Plewa, Stefan Hippler, H. Bonnet, Feng Gao, Eric Gendron, Th. Henning, Gérard Rousset, N. M. Förster Schreiber, Thomas Ott, Johana Panduro, Jean-Philippe Berger, P. Guajardo, Frank Eisenhauer, Karine Perraut, S. von Fellenberg, Yann Clénet, P. T. de Zeeuw, Felix Widmann, Pierre Léna, Thibaut Paumard, Oliver Pfuhl, Xavier Haubois, Erich Wiezorrek, V. Coudé du Foresto, Casey Deen, Sylvestre Lacour, Stefan Gillessen, Jason Dexter, Amiel Sternberg, Gilles Duvert, Matthew Horrobin, Odele Straub, J.-B. Le Bouquin, Armin Huber, Reinhard Genzel, Paulo J. V. Garcia, Sebastian Rabien, António Amorim, G. Rodríguez-Coira, Wolfgang Brandner, Frederic H. Vincent, Roberto Abuter, V. Lapeyrère, Idel Waisberg, Andreas Eckart, S. Yazici, Maryam Habibi, M. Bauböck, Pierre Kervella, Magdalena Lippa, A. Jiménez-Rosales, Ekkehard Wieprecht, European Southern Observatory (ESO), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, 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 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), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Extraterrestrial Physics (MPE), Laboratoire de Physique Statistique de l'ENS (LPS), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Transport et Environnement (INRETS/LTE), Institut National de Recherche sur les Transports et leur Sécurité (INRETS), Institut de biologie et chimie des protéines [Lyon] (IBCP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Swedish Space Corporation (SSC), School of Physics and Astronomy [Tel Aviv], Tel Aviv University [Tel Aviv], Laboratoire Univers et Théories (LUTH (UMR_8102)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Universität zu Köln, AUTRES, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), 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), 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 Paris Diderot - Paris 7 (UPD7)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), 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), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, Gravitation, Telescope, General Relativity and Quantum Cosmology, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Circular orbit, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], Solar mass, 010308 nuclear & particles physics, Astronomy and Astrophysics, Polarization (waves), Astrophysics - Astrophysics of Galaxies, Interferometry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Orbital motion, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Schwarzschild radius
Abstract: We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states ('flares') of its variable near- infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 micro-arcseconds over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(+/-15)-minute period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized 'hot spot' of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild-Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field., Comment: accepted by A&A; 16 pages
Published: 2018
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39. Physical parameters and ±0.2% parallax of the detached eclipsing binary V923 Scorpii

Author: Matthew Horrobin, Casey Deen, W. W. Weiss, A. F. J. Moffat, Slavek M. Rucinski, Paulo J. V. Garcia, Oliver Pfuhl, J. M. Matthews, Odele Straub, Pierre Kervella, A. Mérand, C. Cameron, T. Pribulla, European Southern Observatory (ESO), 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), Galaxies, Etoiles, Physique, Instrumentation (GEPI), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), School of engineering sciences, University of Southampton, Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Department of Physics and Astronomy [Toronto], York University [Toronto], Laboratoire Univers et Théories (LUTH (UMR_8102)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), 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), 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), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Physics, [PHYS]Physics [physics], Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, 010309 optics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Parallax, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS
Abstract: V923 Sco is a bright ($V$ = 5.91), nearby ($\pi$ = 15.46$\pm$0.40 mas) southern eclipsing binary. Because both components are slow rotators, the minimum masses of the components are known with 0.2% precision from spectroscopy. The system seems ideal for very precise mass, radius, and luminosity determinations and, owing to its proximity and long orbital period ($\sim$ 34.8 days), promises to be resolved with long-baseline interferometry. The principal aim is very accurate determinations of absolute stellar parameters for both components of the eclipsing binary and a model-independent determination of the distance.} New high-precision photometry of both eclipses of V923 Sco with the MOST satellite was obtained. The system was spatially resolved with the VLTI AMBER, PIONIER, and GRAVITY instruments at nine epochs. Combining the projected size of the spectroscopic orbit (in km) and visual orbit (in mas) the distance to the system is derived. Simultaneous analysis of photometric, spectroscopic, and interferometric data was performed to obtain a robust determination of the absolute parameters. Very precise absolute parameters of the components were derived in spite of the parameter correlations. The primary component is found to be overluminous for its mass. Combining spectroscopic and interferometric observations enabled us to determine the distance to V923 Sco with better than 0.2% precision, which provides a stringent test of Gaia parallaxes. It is shown that combining spectroscopic and interferometric observations of nearby eclipsing binaries can lead to extremely accurate parallaxes and stellar parameters., Comment: 10 pages, 4 figures, A&A in press
Published: 2018
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40. Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole

Author: R.-R. Rohloff, Andreas Eckart, Sarah Kendrew, Maryam Habibi, Joany Andreina Manjarres Ramos, S. Kellner, Nicolas Blind, D. Ziegler, Wolfgang Brandner, Casey Deen, Bernard Lazareff, Jean-Philippe Berger, Gérard Zins, M. Haug, A. Ramirez, Eric Gendron, F. Haußmann, Thomas Ott, E. Müler, Silvia Scheithauer, Jason Spyromilio, Andreas Kaufer, Xavier Haubois, Markus Schöller, Eckhard Sturm, C. Collin, Stefan Hippler, Laurent Jocou, Myriam Benisty, Julien Woillez, Linda J. Tacconi, A. Buron, Imke Wank, S. von Fellenberg, M. Wiest, Paulo Gordo, Luca Pasquini, Pierre Kervella, L. Palanca, Magdalena Lippa, Martin Kulas, Roderick Dembet, Gilles Duvert, Z. Hubert, Jason Dexter, Yann Clénet, P. T. de Zeeuw, C. Rau, A. Jimenez Rosales, H. Bonnet, Sylvestre Lacour, Guy Perrin, Odele Straub, P. Fédou, J.-B. Le Bouquin, Christian Straubmeier, S. Yazici, Ekkehard Wieprecht, Gérard Rousset, V. Lapeyrère, N. M. Förster Schreiber, Sebastian Rabien, Felix Widmann, Th. Henning, F. Delplancke-Ströbele, M. Bauböck, F. Chapron, Frank Eisenhauer, Gert Finger, R. Garcia Lopez, G. Rodríguez-Coira, Reinhard Genzel, Frederic H. Vincent, Pierre Léna, Thibaut Paumard, Narsireddy Anugu, Idel Waisberg, J. Sanchez-Bermudez, N. Schuler, Karine Perraut, P. M. Plewa, Paulo J. V. Garcia, António Amorim, Yitping Kok, Oliver Pfuhl, Lieselotte Jochum, V. dCoudé u Foresto, Matthew Horrobin, Udo Neumann, Rainer Lenzen, Erich Wiezorrek, Antoine Mérand, Konrad R. W. Tristram, Norbert Hubin, Feng Gao, Stefan Gillessen, Roberto Abuter, 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]), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GRAVITY, 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), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), and 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)
Subjects: General relativity, black hole physics, FOS: Physical sciences, Astrophysics, Physics - Classical Physics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, General Relativity and Quantum Cosmology, Gravitation, Gravitational field, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Very Large Telescope, Galaxy: center, 010308 nuclear & particles physics, Classical Physics (physics.class-ph), Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Black hole, Space and Planetary Science, gravitation, Astrophysics of Galaxies (astro-ph.GA), [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Schwarzschild radius, Gravitational redshift
Abstract: The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A* is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU, ~1400 Schwarzschild radii, the star has an orbital speed of ~7650 km/s, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z ~ 200 km/s / c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 +/- 0.09 (stat) +\- 0.15 (sys). The S2 data are inconsistent with pure Newtonian dynamics., Comment: Accepted for publication in A&A Letters, 29 June 2018, 10 pages, 6 figures, corresponding author: F. Eisenhauer
Published: 2018
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41. GRAVITY chromatic imaging of η Car's core. Milliarcsecond resolution imaging of the wind-wind collision zone (Brγ, He I)

Author: S. Kellner, Pierre Kervella, Faustine Cantalloube, Johana Panduro, Magdalena Lippa, V. Coudé du Foresto, Y. Clénet, R. Abuter, G. Avila, Matteo Accardo, Konrad R. W. Tristram, Dan Popovic, Alejandra Rosales, A. Buron, R. Genzel, C. Deen, Laurent Jocou, Markus Schöller, T. Ott, H. Bonnet, P. Fédou, Frank Eisenhauer, R. van Boekel, Stefan Hippler, André Müller, Pierre Léna, Thibaut Moulin, Julien Woillez, L. Pallanca, Ekkehard Wieprecht, P.-O. Petrucci, N. Hubin, Leander Mehrgan, Sylvestre Lacour, Markus Wittkowski, Vincent Lapeyrere, Christian A. Hummel, M. Haug, Eckhard Sturm, Frederic Derie, Thanh Phan Duc, Sarah Kendrew, Burkhard Wolff, Mario Kiekebusch, Nicolas Blind, Andreas Kaufer, W. J. de Wit, Feng Gao, C. Collin, Silvia Scheithauer, L. Kern, Roderick Dembet, Matthew Horrobin, J.-U. Pott, Stefan Gillessen, Johann Kolb, Narsireddy Anugu, R.-R. Rohloff, M. Riquelme, J. Sanchez-Bermudez, Andreas Eckart, J. Moreno-Ventas, R. Brast, Z. Hubert, Isabelle Percheron, M. Mellein, F. Delplancke-Ströbele, M. Karl, Udo Neumann, Imke Wank, Rainer Lenzen, Odele Straub, Michael Esselborn, Armin Huber, J.-B. Le Bouquin, Ralf Klein, Juan-Luis Ramos, Erich Wiezorrek, Samuel Lévêque, K. Perraut, Frédéric Cassaing, C. E. Garcia Dabo, F. Müller, P. M. Plewa, Ewald Müller, N. Ventura, F. Chapron, Gerd Weigelt, M. Ebert, Martin Kulas, M. Wiest, Elodie Choquet, Luca Pasquini, A. Caratti o Garatti, A. Pflüger, T. de Zeeuw, Guy Perrin, Myriam Benisty, Yves Magnard, Joachim M. Bestenlehner, S. Oberti, António Amorim, Nicolas Schuhler, B. Lazareff, Paulo J. V. Garcia, Jason Dexter, Christian Straubmeier, Th. Henning, Jason Spyromilio, F. H. Vincent, A. Mérand, Senol Yazici, Felix Widmann, C. Rau, Pierre Bourget, R. J. García López, Xavier Haubois, Eric Gendron, Gérard Zins, G. Rousset, Andres J. Ramirez, Gilles Duvert, T. Paumard, Lieselotte Jochum, Idel Waisberg, F. Haussmann, O. Pfuhl, Sebastian Rabien, G. Rodríguez-Coira, Gerd Jakob, J. P. Berger, Wolfgang Brandner, D. Ziegler, and Marcos Suarez
Subjects: Physics, 010308 nuclear & particles physics, Binary number, Astronomy and Astrophysics, Astrophysics, Collision, 01 natural sciences, Galaxy, Wavelength, 13. Climate action, Space and Planetary Science, Angular diameter, 0103 physical sciences, Radiative transfer, Chromatic scale, 010303 astronomy & astrophysics, Cavity wall
Abstract: Context. η Car is one of the most intriguing luminous blue variables in the Galaxy. Observations and models of the X-ray, ultraviolet, optical, and infrared emission suggest a central binary in a highly eccentric orbit with a 5.54 yr period residing in its core. 2D and 3D radiative transfer and hydrodynamic simulations predict a primary with a dense and slow stellar wind that interacts with the faster and lower density wind of the secondary. The wind-wind collision scenario suggests that the secondary’s wind penetrates the primary’s wind creating a low-density cavity in it, with dense walls where the two winds interact. However, the morphology of the cavity and its physical properties are not yet fully constrained. Aims. We aim to trace the inner ∼5–50 au structure of η Car’s wind-wind interaction, as seen through Brγ and, for the first time, through the He I 2s-2p line. Methods. We have used spectro-interferometric observations with the K-band beam-combiner GRAVITY at the VLTI. The analyses of the data include (i) parametrical model-fitting to the interferometric observables, (ii) a CMFGEN model of the source’s spectrum, and (iii) interferometric image reconstruction. Results. Our geometrical modeling of the continuum data allows us to estimate its FWHM angular size close to 2 mas and an elongation ratio ϵ = 1.06 ± 0.05 over a PA = 130° ± 20°. Our CMFGEN modeling of the spectrum helped us to confirm that the role of the secondary should be taken into account to properly reproduce the observed Brγ and He I lines. Chromatic images across the Brγ line reveal a southeast arc-like feature, possibly associated to the hot post-shocked winds flowing along the cavity wall. The images of the He I 2s-2p line served to constrain the 20 mas (∼50 au) structure of the line-emitting region. The observed morphology of He I suggests that the secondary is responsible for the ionized material that produces the line profile. Both the Brγ and the He I 2s-2p maps are consistent with previous hydrodynamical models of the colliding wind scenario. Future dedicated simulations together with an extensive interferometric campaign are necessary to refine our constraints on the wind and stellar parameters of the binary, which finally will help us predict the evolutionary path of η Car.
Published: 2018

42. Accurate ray tracing of realistic neutron star atmospheres for constraining their parameters

Author: Eric Gourgoulhon, Agnieszka Majczyna, Odele Straub, Thibaut Paumard, L. Zdunik, Pawel Haensel, M. Bejger, Jerzy Madej, Agata Różańska, M. Fortin, Frederic H. Vincent, B. Beldycki, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-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 Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Univers et Théories ( LUTH ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: Equation of state, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Context (language use), General Relativity and Quantum Cosmology (gr-qc), 01 natural sciences, Spectral line, General Relativity and Quantum Cosmology, [ PHYS.GRQC ] Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Gravitation, stars: neutron, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, equation of state, relativistic processes, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spacetime, 010308 nuclear & particles physics, Astronomy and Astrophysics, Observable, Computational physics, Neutron star, 13. Climate action, Space and Planetary Science, gravitation, radiative transfer, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract: Thermal dominated X-ray spectra of neutron stars in quiescent transient X-ray binaries and neutron stars that undergo thermonuclear bursts are sensitive to mass and radius. The mass-radius relation of neutron stars depends on the equation of state that governs their interior. Constraining this relation accurately is thus of fundamental importance to understand the nature of dense matter. In this context we introduce a pipeline to calculate realistic model spectra of rotating neutron stars with hydrogen and helium atmospheres. An arbitrarily fast rotating neutron star with a given equation of state generates the spacetime in which the atmosphere emits radiation. We use the Lorene/nrotstar code to compute the spacetime numerically and the ATM24 code to solve the radiative transfer equations self-consistently. Emerging specific intensity spectra are then ray-traced through the neutron star's spacetime from the atmosphere to a distant observer with the Gyoto code. Here, we present and test our fully relativistic numerical pipeline. To discuss and illustrate the importance of realistic atmosphere models we compare our model spectra to simpler models like the commonly used isotropic color-corrected blackbody emission. We highlight the importance of considering realistic model-atmosphere spectra together with relativistic ray tracing to obtain accurate predictions. We also insist on the crucial impact of the star's rotation on the observables. Finally, we close a controversy that has been appearing in the literature in the recent years regarding the validity of the ATM24 code., 17 pages, 13 figures; accepted in ApJ ; important updates in Section 2.2 and Fig. 2
Published: 2017
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43. High-frequency and type-C QPOs from oscillating, precessing hot, thick flow

Author: Omer Blaes, P. Chris Fragile, Odele Straub, Laboratoire Univers et Théories (LUTH (UMR_8102)), 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)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], Accretion (meteorology), 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Extrapolation, FOS: Physical sciences, Astronomy and Astrophysics, Radius, Astrophysics, 01 natural sciences, Black hole, Space and Planetary Science, 0103 physical sciences, Epicyclic frequency, Thick disk, Precession, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Spin-½
Abstract: Motivated by recent studies showing an apparent correlation between the high-frequency quasi-periodic oscillations (QPOs) and the low-frequency, type-C QPO in low-mass, black hole X-ray binaries (LMXBs), we explore a model that explains all three QPOs in terms of an oscillating, precessing hot flow in the truncated-disk geometry. Our model favors attributing the two high-frequency QPOs, often occurring in a near 3:2 frequency ratio, to the breathing and vertical epicyclic frequency modes of the hot, thick flow, although we can not rule out the Keplerian and m=-1 radial epicyclic modes. In either case, the type-C QPO is attributed to precession. The correlation of the QPOs comes from the fact that all three frequencies are associated with the same geometrical structure. While the exact QPO frequencies are sensitive to the black hole mass and spin, their evolution over the course of an outburst is mainly tied to the truncation radius between the geometrically thin, optically thick disk and the inner, hot flow. We show that, in the case of the LMXB GRO J1655-40, this model can explain the one simultaneous observation of all three QPOs and that an extrapolation of the model appears to match lower frequency observations where only two of the three components are seen. Thus, this model may be able to unify multiple QPO observations using the properties of a single, simple, geometrical model., Comment: 7 pages, 4 figures, accepted to MNRAS
Published: 2016
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44. Imaging a boson star at the Galactic center

Author: Frederic H. Vincent, Zakaria Meliani, P Grandclément, Eric Gourgoulhon, Odele Straub, 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), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), 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), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics and Astronomy (miscellaneous), Event horizon, General relativity, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Compact star, 01 natural sciences, General Relativity and Quantum Cosmology, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, Galactic Center, Accretion (astrophysics), Galaxy, Black hole, Stars, [SDU]Sciences of the Universe [physics], Astrophysics - High Energy Astrophysical Phenomena
Abstract: Millimeter very long baseline interferometry will soon produce accurate images of the closest surroundings of the supermassive compact object at the center of the Galaxy, Sgr A*. These images may reveal the existence of a central faint region, the so-called shadow, which is often interpreted as the observable consequence of the event horizon of a black hole. In this paper, we compute images of an accretion torus around Sgr A* assuming this compact object is a boson star, i.e. an alternative to black holes within general relativity, with no event horizon and no hard surface. We show that very relativistic rotating boson stars produce images extremely similar to Kerr black holes, showing in particular shadow-like and photon-ring-like structures. This result highlights the extreme difficulty of unambiguously telling the existence of an event horizon from strong-field images., 21 pages, 9 figures, accepted in CQG; main difference wrt previous version is the last paragraph of the conclusion
Published: 2016
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45. The Polish doughnuts revisited

Author: P. C. Fragile, Jiří Horák, Marek A. Abramowicz, Mami Machida, Lei Qian, and Odele Straub
Subjects: Physics, Angular momentum, Classical mechanics, Accretion disc, Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), FOS: Physical sciences, Entropy (information theory), Astronomy and Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We construct a new family of analytic models of black hole accretion disks in dynamical equilibria. Our construction is based on assuming distributions of angular momentum and entropy. For a particular choice of the distribution of angular momentum, we calculate the shapes of equipressure surfaces. The equipressure surfaces we find are similar to those in thick, slim and thin disks, and to those in ADAFs., Comment: 7 pages, 5 figures, accepted for publication in Astronomy & Astrophysics
Published: 2009
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46. Testing wind as an explanation for the spin problem in the continuum-fitting method

Author: Odele Straub, Bei You, Michal Bursa, Bozena Czerny, Agata Różańska, Michal Dovciak, Malgosia Sobolewska, Laboratoire Univers et Théories (LUTH (UMR_8102)), 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)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories ( LUTH ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, black hole physics, Binary number, FOS: Physical sciences, 01 natural sciences, Spectral line, Accretion rate, X-rays: binaries, Accretion disc, accretion, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Continuum (measurement), 010308 nuclear & particles physics, accretion disks, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Accretion (astrophysics), Computational physics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Parametric model, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The continuum-fitting method is one of the two most advanced methods of determining the black hole spin in accreting X-ray binary systems. There are, however, still some unresolved issues with the underlying disk models. One of them manifests as an apparent decrease in spin for increasing source luminosity. Here, we perform a few simple tests to establish whether outflows from the disk close to the inner radius can address this problem. We employ four different parametric models to describe the wind and compare these to the apparent decrease in spin with luminosity measured in the sources LMC~X-3 and GRS~1915+105. Wind models in which parameters do not explicitly depend on the accretion rate cannot reproduce the spin measurements. Models with mass accretion rate dependent outflows, however, have spectra that emulate the observed ones. The assumption of a wind thus effectively removes the artifact of spin decrease. This solution is not unique; the same conclusion can be obtained with a truncated inner disk model. To distinguish among valid models, high resolution X-ray data and a realistic description of the Comptonization in the wind will be needed., 14 pages, 11 figures, accepted by ApJ
Published: 2016
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47. GR-AMRVAC code applications: accretion onto compact objects, boson stars versus black holes

Author: P. Grandclément, F. Casse, Odele Straub, F. Dauvergne, Zakaria Meliani, Frederic H. Vincent, Laboratoire Univers et Théories (LUTH (UMR_8102)), 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), AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Meudon (OBSPM), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), 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)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and Silesian University in Opava
Subjects: Physics, Physics and Astronomy (miscellaneous), 010308 nuclear & particles physics, Strong gravity, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, Compact star, 01 natural sciences, Accretion (astrophysics), Neutron star, General Relativity and Quantum Cosmology, Intermediate-mass black hole, 0103 physical sciences, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Stellar black hole, 010303 astronomy & astrophysics, Schwarzschild radius, Gamma-ray burst progenitors
Abstract: International audience; In the close vicinity of a compact object strong gravity imprints its signature onto matter. Systems that contain at least one compact object are observed to exhibit extreme physical properties and typically emit highly energetic radiation. The nature of the compact objects that produce the strongest gravitational fields is to date not settled. General relativistic numerical simulations of fluid dynamics around black holes, neutron stars, and other compact objects such as boson stars (BSs) may give invaluable insights into this fundamental question. In order to study the behavior of fluid in the strong gravity regime of an arbitrary compact object we develop a new general relativistic hydrodynamics code. To this end we extend the existing versatile adaptive mesh refinement code MPI-AMRVAC into a general relativistic hydrodynamics framework and adapt it for the use of numerically given spacetime metrics. In the present article we study accretion flows in the vicinity of various types of BSs whose numerical metrics are calculated by the KADATH spectral solver library. We design specific tests to check the reliability of any code intending to study BSs and compare the solutions with those obtained in the context of Schwarzschild black holes. We perform the first ever general relativistic hydrodynamical simulations of gas accretion by a BS. The behavior of matter at small distances from the center of a BS differs notably from the black hole case. In particular we demonstrate that in the context of Bondi spherical accretion the mass accretion rate onto non-rotating BSs remains constant whereas it increases for Schwarzschild black holes. We also address the scenario of non-spherical accretion onto BSs and show that this may trigger mass ejection from the interior of the BS. This striking feature opens the door to forthcoming investigations regarding accretion-ejection flows around such types of compact objects.
Published: 2016
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48. Circular geodesics and thick tori around rotating boson stars

Author: Frederic H. Vincent, Odele Straub, P. Grandclément, R. Monceau-Baroux, Zakaria Meliani, Eric Gourgoulhon, Laboratoire Univers et Théories (LUTH (UMR_8102)), 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), Hôpital Avicenne [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), 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, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Hôpital avicenne, Assistance publique - Hôpitaux de Paris (AP-HP) (APHP)-Université Paris 13 (UP13)-Hôpital Avicenne, 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), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Angular momentum, Physics and Astronomy (miscellaneous), FOS: Physical sciences, Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Specific relative angular momentum, General Relativity and Quantum Cosmology, Gravitation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, Boson, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], 010308 nuclear & particles physics, Torus, Accretion (astrophysics), Black hole, Stars, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract: Accretion disks play an important role in the evolution of their relativistic inner compact objects. The emergence of a new generation of interferometers will allow to resolve these accretion disks and provide more information about the properties of the central gravitating object. Due to this instrumental leap forward it is crucial to investigate the accretion disk physics near various types of inner compact objects now to deduce later constraints on the central objects from observations. A possible candidate for the inner object is the boson star. Here, we will try to analyze the differences between accretion structures surrounding boson stars and black holes. We aim at analysing the physics of circular geodesics around boson stars and study simple thick accretion tori (so-called Polish doughnuts) in the vicinity of these stars. We realize a detailed study of the properties of circular geodesics around boson stars. We then perform a parameter study of thick tori with constant angular momentum surrounding boson stars. This is done using the boson star models computed by a code constructed with the spectral solver library KADATH. We demonstrate that all the circular stable orbits are bound. In the case of a constant angular momentum torus, a cusp in the torus surface exists only for boson stars with a strong gravitational scalar field. Moreover, for each inner radius of the disk, the allowed specific angular momentum values lie within a constrained range which depends on the boson star considered. We show that the accretion tori around boson stars have different characteristics than in the vicinity of a black hole. With future instruments it could be possible to use these differences to constrain the nature of compact objects., Accepted for publication in CQG
Published: 2015
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49. Investigating the mass of the intermediate mass black hole candidate HLX-1 with the slimbh model

Author: Olivier Godet, Mathieu Servillat, Natalie A. Webb, Didier Barret, Odele Straub, Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), 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), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), 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), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), 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 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), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), and 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)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, Spectral line, Luminosity, General Relativity and Quantum Cosmology, X-rays: binaries, accretion, 0103 physical sciences, HLX-1, Continuum (set theory), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Photosphere, 010308 nuclear & particles physics, accretion disks, Astronomy and Astrophysics, Galaxy, Black hole, Space and Planetary Science, Intermediate-mass black hole, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: In this paper we present a comprehensive study of the mass of the intermediate mass black hole candidate HLX-1 in the galaxy ESO 243-49. We analyse the continuum X-ray spectra collected by Swift, XMM-Newton, and Chandra with the slim disc model, SLIMBH, and estimate the black hole mass for the full range of inclination (inc = 0{\deg} - 85{\deg}) and spin (a* = 0 - 0.998). The relativistic SLIMBH model is particularly suited to study high luminosity disc spectra as it incorporates the effects of advection, such as the shift of the inner disc edge towards smaller radii and the increasing height of the disc photosphere (including relativistic ray-tracing from its proper location rather than the mid-plane of the disc). We find for increasing values of inclination that a zero spin black hole has a mass range of 6,300 - 50,900 M_sun and a maximally spinning black hole has a mass between 16,900 - 191,700 M_sun. This is consistent with previous estimates and reinforces the idea that HLX-1 contains an intermediate mass black hole., Comment: updated version, published in Astronomy and Astrophysics
Published: 2014
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50. The Low-Spin Black Hole in LMC X-3

Author: Charles D. Bailyn, Jerome A. Orosz, M. Kolehmainen, Jeffrey E. McClintock, James F. Steiner, Ronald A. Remillard, Odele Straub, Sub-department of Astrophysics [Oxford], Department of Physics [Oxford], University of Oxford [Oxford]-University of Oxford [Oxford], Laboratoire Univers et Théories (LUTH (UMR_8102)), 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)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Physics, [PHYS]Physics [physics], High Energy Astrophysical Phenomena (astro-ph.HE), Accretion (meteorology), Astrophysics::High Energy Astrophysical Phenomena, Spectrum (functional analysis), Binary number, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Measure (mathematics), Spectral line, Black hole, Stars, General Relativity and Quantum Cosmology, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS, Spin-½
Abstract: Building upon a new dynamical model for the X-ray binary LMC X-3, we measure the spin of its black hole primary via the continuum-fitting method. We consider over one thousand thermal-state RXTE X-ray spectra of LMC X-3. Using a large subset of these spectra, we constrain the spin parameter of the black hole to be spin = 0.21(+0.18,-0.22), 90% confidence. Our estimate of the uncertainty in spin takes into account a wide range of systematic errors. We discuss evidence for a correlation between a black hole's spin and the complexity of its X-ray spectrum., Comment: Submitted to ApJL, 5 pages emulateapj, 2 figures and 1 table
Published: 2014
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