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288 results on '"Alencar, S. H. P."'

51. The magnetic field and multiple planets of the young dwarf AU Mic

Author

Donati, J-F, primary, Cristofari, P I, additional, Finociety, B, additional, Klein, B, additional, Moutou, C, additional, Gaidos, E, additional, Cadieux, C, additional, Artigau, E, additional, Correia, A C M, additional, Boué, G, additional, Cook, N J, additional, Carmona, A, additional, Lehmann, L T, additional, Bouvier, J, additional, Martioli, E, additional, Morin, J, additional, Fouqué, P, additional, Delfosse, X, additional, Doyon, R, additional, Hébrard, G, additional, Alencar, S H P, additional, Laskar, J, additional, Arnold, L, additional, Petit, P, additional, Kóspál, Á, additional, Vidotto, A, additional, Folsom, C P, additional, and collaboration, the S L S, additional

Published
2023
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52. Stable accretion and episodic outflows in the young transition disk system GM Aurigae : A semester-long optical and near-infrared spectrophotometric monitoring campaign

Author

Bouvier, J., Sousa, A., Pouilly, Kim, Almenara, J. M., Donati, J. -F, Alencar, S. H. P., Frasca, A., Grankin, K., Carmona, A., Pantolmos, G., Zaire, B., Bonfils, X., Bayo, A., Rebull, L. M., Alonso-Santiago, J., Gameiro, J. F., Cook, N. J., Artigau, E., Bouvier, J., Sousa, A., Pouilly, Kim, Almenara, J. M., Donati, J. -F, Alencar, S. H. P., Frasca, A., Grankin, K., Carmona, A., Pantolmos, G., Zaire, B., Bonfils, X., Bayo, A., Rebull, L. M., Alonso-Santiago, J., Gameiro, J. F., Cook, N. J., and Artigau, E.

Abstract

Context: Young stellar systems actively accrete from their circumstellar disk and simultaneously launch outflows. The physical link between accretion and ejection processes remains to be fully understood. Aims: We investigate the structure and dynamics of magnetospheric accretion and associated outflows on a scale smaller than 0.1 au around the young transitional disk system GM Aur. Methods: We devised a coordinated observing campaign to monitor the variability of the system on timescales ranging from days to months, including partly simultaneous high-resolution optical and near-infrared spectroscopy, multiwavelength photometry, and low-resolution near-infrared spectroscopy, over a total duration of six months, covering 30 rotational cycles. We analyzed the photometric and line profile variability to characterize the accretion and ejection processes. Results: The optical and near-infrared light curves indicate that the luminosity of the system is modulated by surface spots at the stellar rotation period of 6.04 +/- 0.15 days. Part of the Balmer, Paschen, and Brackett hydrogen line profiles as well as the HeI 5876 angstrom and HeI 10830 angstrom line profiles are modulated on the same period. The Pa beta line flux correlates with the photometric excess in the u ' band, which suggests that most of the line emission originates from the accretion process. High-velocity redshifted absorptions reaching below the continuum periodically appear in the near-infrared line profiles at the rotational phase in which the veiling and line fluxes are the largest. These are signatures of a stable accretion funnel flow and associated accretion shock at the stellar surface. This large-scale magnetospheric accretion structure appears fairly stable over at least 15 and possibly up to 30 rotational periods. In contrast, outflow signatures randomly appear as blueshifted absorption components in the Balmer and HeI 10830 angstrom line profiles. They are not rotationally modulated and disappe

Published
2023
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53. Monitoring the young planet host V1298 Tau with SPIRou: planetary system and evolving large-scale magnetic field.

Author

Finociety, B, Donati, J-F, Cristofari, P I, Moutou, C, Cadieux, C, Cook, N J, Artigau, E, Baruteau, C, Debras, F, Fouqué, P, Bouvier, J, Alencar, S H P, Delfosse, X, Grankin, K, Carmona, A, Petit, P, Kóspál, Á, and consortium, the SLS/SPICE

Subjects
MAGNETIC fields, STELLAR rotation, INNER planets, PLANETS, STELLAR magnetic fields, PLANETARY systems, CONFIDENCE intervals
Abstract

We report results of a spectropolarimetric monitoring of the young Sun-like star V1298 Tau based on data collected with the near-infrared spectropolarimeter SPIRou at the Canada–France–Hawaii Telescope between late 2019 and early 2023. Using Zeeman–Doppler Imaging and the Time-dependent Imaging of Magnetic Stars methods on circularly polarized spectra, we reconstructed the large-scale magnetic topology of the star (and its temporal evolution), found to be mainly poloidal and axisymmetric with an average strength varying from 90 to 170 G over the ∼3.5 yr of monitoring. The magnetic field features a dipole whose strength evolves from 85 to 245 G, and whose inclination with respect to the stellar rotation axis remains stable until 2023 where we observe a sudden change, suggesting that the field may undergo a polarity reversal, potentially similar to those periodically experienced by the Sun. Our data suggest that the differential rotation shearing the surface of V1298 Tau is about 1.5 times stronger than that of the Sun. When coupling our data with previous photometric results from K2 and TESS and assuming circular orbits for all four planets, we report a 3.9σ detection of the radial velocity signature of the outermost planet (e), associated with a most probable mass, density, and orbital period of |$M_\mathrm{e}=0.95^{+0.33}_{-0.24}$| MꝜ, |$\rho _\mathrm{e}=1.66^{+0.61}_{-0.48}$| |$\rm g\, cm^{-3}$|⁠ , and P e = 53.0039 ± 0.0001 d, respectively. For the three inner planets, we only derive 99 per cent confidence upper limits on their mass of 0.44, 0.22, and 0.25 MꝜ, for b, c, and d, respectively. [ABSTRACT FROM AUTHOR]

Published
2023
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54. Magnetic fields and rotation periods of M dwarfs from SPIRou spectra.

Author

Donati, J-F, Lehmann, L T, Cristofari, P I, Fouqué, P, Moutou, C, Charpentier, P, Ould-Elhkim, M, Carmona, A, Delfosse, X, Artigau, E, Alencar, S H P, Cadieux, C, Arnold, L, Petit, P, Morin, J, Forveille, T, Cloutier, R, Doyon, R, Hébrard, G, and SLS, the Collaboration

Subjects
MAGNETIC fields, KRIGING, ROSSBY number, ROTATIONAL motion, STELLAR rotation, DWARF stars
Abstract

We present near-infrared spectropolarimetric observations of a sample of 43 weakly to moderately active M dwarfs, carried with SPIRou at the Canada–France–Hawaii Telescope in the framework of the SPIRou Legacy Survey from early 2019 to mid-2022. We use the 6700 circularly polarised spectra collected for this sample to investigate the longitudinal magnetic field and its temporal variations for all sample stars, from which we diagnose, through quasi-periodic Gaussian process regression, the periodic modulation and longer-term fluctuations of the longitudinal field. We detect the large-scale field for 40 of our 43 sample stars, and infer a reliable or tentative rotation period for 38 of them, using a Bayesian framework to diagnose the confidence level at which each rotation period is detected. We find rotation periods ranging from 14 to over 60 d for the early-M dwarfs, and from 70 to 200 d for most mid- and late-M dwarfs (potentially up to 430 d for one of them). We also find that the strength of the detected large-scale fields does not decrease with increasing period or Rossby number for the slowly rotating dwarfs of our sample as it does for higher-mass, more active stars, suggesting that these magnetic fields may be generated through a different dynamo regime than those of more rapidly rotating stars. We also show that the large-scale fields of most sample stars evolve on long time-scales, with some of them globally switching sign as stars progress on their putative magnetic cycles. [ABSTRACT FROM AUTHOR]

Published
2023
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55. The SPIRou legacy survey

Author

Fouqué, P., primary, Martioli, E., additional, Donati, J.-F., additional, Lehmann, L. T., additional, Zaire, B., additional, Bellotti, S., additional, Gaidos, E., additional, Morin, J., additional, Moutou, C., additional, Petit, P., additional, Alencar, S. H. P., additional, Arnold, L., additional, Artigau, É., additional, Cang, T.-Q., additional, Carmona, A., additional, Cook, N. J., additional, Cortés-Zuleta, P., additional, Cristofari, P. I., additional, Delfosse, X., additional, Doyon, R., additional, Hébrard, G., additional, Malo, L., additional, Reylé, C., additional, and Usher, C., additional

Published
2023
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56. Stable accretion and episodic outflows in the young transition disk system GM Aurigae

Author

Bouvier, J., primary, Sousa, A., additional, Pouilly, K., additional, Almenara, J. M., additional, Donati, J.-F., additional, Alencar, S. H. P., additional, Frasca, A., additional, Grankin, K., additional, Carmona, A., additional, Pantolmos, G., additional, Zaire, B., additional, Bonfils, X., additional, Bayo, A., additional, Rebull, L. M., additional, Alonso-Santiago, J., additional, Gameiro, J. F., additional, Cook, N. J., additional, and Artigau, E., additional

Published
2023
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60. The Pre-Main Sequence Spectroscopic Binary AK Sco

Author

Alencar, S. H. P., Vaz, L. P. R., Melo, C. H. F., Dullemond, C. P., Andersen, J., Batalha, C., Mathieu, R. D., Appenzeller, I., Bahcall, J. N., Bertola, F., Cassinelli, J. P., Cesarsky, C. J., Engvold, O., McCray, R., Murdin, P. G., Pacini, F., Radhakrishnan, V., Sato, K., Shu, F. H., Somov, B. V., Sunyaev, R. A., Tanaka, Y., Tremaine, S., Weiss, N.O., Burton, W.B., editor, Kuijpers, J. M. E., editor, Van Den Heuvel, E. P. J., editor, Van Der Laan, H., editor, Lépine, Jacques, editor, and Gregorio-Hetem, Jane, editor

Published
2003
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63. Spectroscopic analysis of accretion/ejection signatures in the Herbig Ae/Be stars

Author

Moura, T, Alencar, S. H. P., and Sousa, A. P

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Time series analysis of two high-resolution UVES / ESO spectra stars Herbig Ae/Be members of the young star cluster NGC 2264 with indications of sufficient circumstellar material so that the addition and ejection processes. Determination of stellar parameters with synthetic spectral adjustment, and study the variability of the emission lines and classified the circumstellar lines, such as Halpha, Hbeta, according to its morphologies. Halpha medium profile model, using a hybrid MHD model that includes a stellar magnetosphere and a disk wind

Published
2021
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68. CUBES: the Cassegrain U-band Efficient Spectrograph

Author

Evans, Christopher J., Bryant, Julia J., Motohara, Kentaro, Cristiani, S., Alcalá, J. M., Alencar, S. H. P., Balashev, S., Bastian, N., Barbuy, B., Battino, U., Calcines, A., Calderone, G., Cambianica, P., Carini, R., Carter, B., Cassisi, S., Castilho, B., Cescutti, G., Christlieb, N., Cirami, R., Coretti, I., Cooke, R. J., Covino, S., Cremonese, G., Cunha, K., Cupani, G., da Silva, A., De Caprio, V., De Cia, A., Dekker, H., D'Elia, V., de Silva, G., Diaz, M. P., Di Marcantonio, P., D'Auria, D., D'Odorico, V., Fitzsimmons, A., Ernandes, H., Evans, C., Franchini, M., Genoni, M., Gänsicke, B., Giribaldi, R. E., Gneiding, C., Grazian, A., Hansen, C. J., La Forgia, F., Landoni, M., Lazzarin, M., Lunney, D., Maciel, W. J., Marcolino, W., Marconi, M., Migliorini, A., Miller, C., Noterdaeme, P., Opitom, C., Pariani, G., Pilecki, B., Piranomonte, S., Quirrenbach, A., Redaelli, E. M. A., Pereira, C., Randich, S., Rossi, S., Sanchez-Janssen, R., Seifert, W., Smiljanic, R., Snodgrass, C., Stilz, I., Stürmer, J., Vanzella, E., Ventura, P., Verducci, O., Waring, C., Watson, S., Wells, M., Wright, D., Zafar, T., and Zanutta, A.

Published
2022
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69. Magnetospheric accretion in the intermediate-mass T Tauri Star HQ Tau

Author

Pouilly, K., Bouvier, J., Evelyne Alecian, M Cody, A., F Donati, J., Alencar, S. H. P., Grankin, K., Rebull, L., Folsom, C., 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]), and European Project: 742095,SPIDI

Subjects
Classical T Tauri Star, IMTTS, HQ Tau, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], hot spot, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, cold spot, magnetospheric accretion
Abstract

International audience; Magnetospheric accretion is a main interaction process between Classical T Tauri stars (CTTSs) and their inner disk. Understanding this process is therefore crucial to characterize star-disk interactions. We investigate the photometric and spectroscopic variability of HQ Tau, a CTTS of 1.8 M_⊙ and 2.7 R_⊙, from Kepler K2 light curve and a series of ESPaDOnS spectra obtained at the Canada-France-Hawaii Telescope. Balmer line profiles exhibit periodic variability, at the stellar rotation period, with high velocity redshifted absorptions appearing (Inverse P Cygni Profile - IPC). The radial velocity shows a modulation at the stellar rotation period too, but is not consistent with the time of appearance of the IPC. We therefore ascribed the radial velocity modulation to a cold spot and the IPC to the accretion column. From the spectropolarimetric analysis of the ESPaDOnS spectra , we also measure a mean longitudinal magnetic field with a maximum intensity of 430 G, which is modulated by stellar rotation. The maximum is consistent with the IPC, we deduce that the mean longitudinal magnetic field is modulated by the hot spot thus corresponds to the footprint of the magnetic pole at the stellar surface. Preliminary results of this study appear to be consistent with what is expected from magnetospheric accretion onto a global dipolar magnetic field in the intermediate-mass T Tauri star HQ Tau.

Published
2019

70. The magnetosphere of the close accreting PMS binary V4046 Sgr

Author

Gregory S. G., Holzwarth V. R., Donati J.-F., Hussain G. A. J., Montmerle T., Alecian E., Alencar S. H. P., Argiroffi C., Audard M., Bouvier J., Damiani F., Güdel M., Huenemoerder D. P., Kastner J. H., Maggio A., Sacco G. G., and Wade G. A.

Subjects
Physics, QC1-999
Abstract

V4046 Sagittarii AB is a close short-period classical T Tauri binary. It is a circularised and synchronised system accreting from a circumbinary disk. In 2009 it was observed as part of a coordinated program involving near-simultaneous spectropolarimetric observations with ESPaDOnS at the Canada-France-Hawai’i Telescope and high-resolution X-ray observations with XMM-Newton. Magnetic maps of each star were derived from Zeeman-Doppler imaging. After briefly highlighting the most significant observational findings, we present a preliminary 3D model of the binary magnetosphere constructed from the magnetic maps using a newly developed binary magnetic field extrapolation code. The large-scale fields (the dipole components) of both stars are highly tilted with respect to their rotation axes, and their magnetic fields are linked.

Published
2014
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71. T Tauri star V410 Tau in the eyes of SPIRou and TESS.

Author

Finociety, B, Donati, J-F, Klein, B, Zaire, B, Lehmann, L, Moutou, C, Bouvier, J, Alencar, S H P, Yu, L, Grankin, K, Artigau, É, Doyon, R, Delfosse, X, Fouqué, P, Hébrard, G, Jardine, M, Kóspál, Á, Ménard, F, and consortium, SLS

Subjects
STELLAR activity, RADIAL velocity of stars, KRIGING, YIELD surfaces, STELLAR magnetic fields, MAGNETIC fields
Abstract

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star V410 Tau based on data collected mostly with SPIRou, the near-infrared (NIR) spectropolarimeter recently installed at the Canada-France-Hawaii Telescope , as part of the SPIRou Legacy Survey large programme, and with TESS between October and December 2019. Using Zeeman–Doppler Imaging (ZDI), we obtained the first maps of photospheric brightness and large-scale magnetic field at the surface of this young star derived from NIR spectropolarimetric data. For the first time, ZDI is also simultaneously applied to high-resolution spectropolarimetric data and very-high-precision photometry. V410 Tau hosts both dark and bright surface features and magnetic regions similar to those previously imaged with ZDI from optical data, except for the absence of a prominent dark polar spot. The brightness distribution is significantly less contrasted than its optical equivalent, as expected from the difference in wavelength. The large-scale magnetic field (⁠|${\sim}410$|  G), found to be mainly poloidal, features a dipole of |${\sim}390$|  G, again compatible with previous studies at optical wavelengths. NIR data yield a surface differential rotation slightly weaker than that estimated in the optical at previous epochs. Finally, we measured the radial velocity of the star and filtered out the stellar activity jitter using both ZDI and Gaussian Process Regression down to a precision of |${\sim}0.15$| and 0.08  |$\mathrm{km}\, \mathrm{s}^{-1}$| RMS, respectively, confirming the previously published upper limit on the mass of a potential close-in massive planet around V410 Tau. [ABSTRACT FROM AUTHOR]

Published
2021
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72. Ejection processes in the young open cluster NGC 2264

Author

Mcginnis, P. T., Dougados, Catherine, Alencar, S. H. P., Bouvier, J, Cabrit, Sylvie, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
stars: jets, [PHYS]Physics [physics], accretion, accretion disks, stars: winds, line: formation, stars: pre-main sequence, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], outflows
Abstract

International audience; Context. Statistical studies of the spectral signatures of jets and winds in young stars are crucial to characterize outflows and understand their impact on disk and stellar evolution. The young, open cluster NGC 2264 contains hundreds of well-characterized classical T Tauri stars (CTTS), being thus an ideal site for these statistical studies. Its slightly older age than star forming regions studied in previous works, such as Taurus, allows us to investigate outflows in a different phase of CTTS evolution. Aims: We search for correlations between the [OI]λ6300 line, a well-known tracer of jets and winds in young stars, and stellar, disk and accretion properties in NGC 2264, aiming to characterize the outflow phenomena that occur within the circumstellar environment of young stars. Methods: We analyzed FLAMES spectra of 184 stars, detecting the [OI]λ6300 line in 108 CTTSs and two Herbig AeBe stars. We identified the main features of this line: a high-velocity component (HVC), and a broad and narrow low-velocity components (BLVC and NLVC). We calculated luminosities and kinematic properties of these components, then compared them with known stellar and accretion parameters. Results: The luminosity of the [OI]λ6300 line and its components correlate positively with the stellar and accretion luminosity. The HVC is only detected among systems with optically thick inner disks; the BLVC is most common among thick disk systems and rarer among systems with anemic disks and transition disks; and the NLVC is detected among systems with all types of disks, including transition disks. Our BLVCs present blueshifts of up to 50 km s-1 and widths consistent with disk winds originating between 0.05 and 0.5 au from the central object, while the NLVCs in our sample have widths compatible with an origin between 0.5 and 5 au, in agreement with previous studies in Taurus. A comparison of [OI]λ6300 profiles with CoRoT light curves shows that the HVC is found most often among sources with irregular, aperiodic photometric variability, usually associated with CTTSs accreting in an unstable regime. No stellar properties (Teff, mass, rotation) appear to significantly influence any property of protosellar jets. We find jet velocities on average similar to those found in Taurus. Conclusions: We confirm earlier findings in Taurus which favor an inner MHD disk wind as the origin of the BLVC, while there is no conclusive evidence that the NLVC traces photoevaporative disk winds. The [OI]λ6300 line profile shows signs of evolving as the disk disperses, with the HVC and BLVC disappearing as the inner disk becomes optically thin, in support of the scenario of inside-out gas dissipation in the inner disk. Tables C1-C4 are only available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/620/A87

Published
2018
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73. Transition disk stars in the NGC 2264 cluster - Accretion diagnostic

Author

Sousa, A. P., Alencar, S. H. P., and POTHIER, Nathalie

Subjects
[SDU] Sciences of the Universe [physics], accretion, accretion disks, open clusters and associations: individual: NGC 2264, stars: pre-main sequence
Abstract

Disk holes are inferred from infrared observations of T Tauri stars, indicating the existence of a transitional phase between thick accreting disks and debris disks. Using data from the observational multiwavelength campaign CSI2264, we analyzed 410 stars belonging to NGC 2264 and found about 7% transition disk candidates. We characterized these star-disk systems using accretion diagnostics and we compared them with star-disk systems with full disks and diskless. We were able to evaluate the influence of disk evolution on the observed accretion characteristics.

Published
2018

74. The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264

Author

European Research Council, Leverhulme Trust, Istituto Nazionale di Astrofisica, Ministero dell'Istruzione, dell'Università e della Ricerca, European Science Foundation, Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil), Ministerio de Economía y Competitividad (España), European Commission, Venuti, L., Prisinzano, L., Sacco, G. G., Flaccomio, E., Bonito, R., Damiani, F., Micela, Giusi, Guarcello, M.G., Randich, S., Stauffer, J. R., Cody, A. M., Jeffries, R.D., Alencar, S. H. P., Alfaro, Emilio J., Lanzafame, A.C., Pancino, E., Bayo, A., Carraro, G., Costado, M. T., Frasca, A., Jofré, P., Morbidelli, L., Sousa, S. G., Zaggia, S., European Research Council, Leverhulme Trust, Istituto Nazionale di Astrofisica, Ministero dell'Istruzione, dell'Università e della Ricerca, European Science Foundation, Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil), Ministerio de Economía y Competitividad (España), European Commission, Venuti, L., Prisinzano, L., Sacco, G. G., Flaccomio, E., Bonito, R., Damiani, F., Micela, Giusi, Guarcello, M.G., Randich, S., Stauffer, J. R., Cody, A. M., Jeffries, R.D., Alencar, S. H. P., Alfaro, Emilio J., Lanzafame, A.C., Pancino, E., Bayo, A., Carraro, G., Costado, M. T., Frasca, A., Jofré, P., Morbidelli, L., Sousa, S. G., and Zaggia, S.

Abstract

Context. Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. Aims. We aim to explore the structure of the open cluster and star-forming region NGC 2264 (∼3 Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. Methods. We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8 M and including both disk-bearing and disk-free young stars. We used T estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters. Results. We find a significant age spread of 4-5 Myr among cluster members. Disk-bearing objects are statistically associated with younger isochronal ages than disk-free sources. The cluster has a hierarchical structure, with two main blocks along its latitudinal extension. The northern half develops around the O-type binary star S Mon; the southern half, close to the tip of the Cone Nebula, contains the most embedded regions of NGC 2264, populated mainly by objects with disks and ongoing accretion. The median ages of objects at different locations within the cluster, and the spatial distribution of disked and non-disked sources, suggest that star formation began in the north of the cluster, over 5 Myr ago, and was ignited in its southern region a few Myr later. Star for

Published
2018

75. Modelling the magnetic activity and filtering radial velocity curves of young Suns: the weak-line T Tauri star LkCa 4

Author

Donati, J. -F., Hébrard, Eric, Hussain, G., Moutou, C., Grankin, K., Boisse, I., Morin, Julien, Gregory, S. G., Vidotto, A. A., Bouvier, J., Alencar, S. H. P., Delfosse, X., Doyon, R., Takami, M., Jardine, M. M., Fares, R., Cameron, A. C., Menard, F., Dougados, C., Herczeg, G., Collaboration, The Matysse, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Crimean Astrophysical Observatory (CrAO), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), University of St Andrews [Scotland], Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève = University of Geneva (UNIGE), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Universidade Federal de Minas Gerais [Belo Horizonte] (UFMG), Université de Montréal (UdeM), Academia Sinica, Laboratoire Franco-Chilien d'Astronomie (LFCA), Universidad de Chile = University of Chile [Santiago] (UCHILE)-Pontificia Universidad Católica de Chile (UC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Universidad de Concepción - University of Concepcion [Chile], Kavli Institute for Astronomy and Astrophysics [Beijing] (KIAA-PKU), Peking University [Beijing], MaTYSSE, 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), 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), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Genève (UNIGE), Institut 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), Université de Montréal, 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, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), 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]), 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), Science & Technology Facilities Council, PPARC - Now STFC, and University of St Andrews. School of Physics and Astronomy

Subjects
Brightness, K-type main-sequence star, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, polarimetric [Techniques], 01 natural sciences, Planet, stars: rotation, 0103 physical sciences, Hot Jupiter, QB Astronomy, Differential rotation, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, formation [Stars], QC, stars: individual: LkCa 4, Astrophysics::Galaxy Astrophysics, QB, Physics, stars: formation, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: magnetic field, Astronomy, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: imaging, rotation [Stars], Radial velocity, individual: LkCa 4 [Stars], magnetic field [Stars], Stars, T Tauri star, techniques: polarimetric, QC Physics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, imaging [Stars], Astrophysics::Earth and Planetary Astrophysics
Abstract

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa4 within the MaTYSSE programme, involving ESPaDOnS at the Canada-France-Hawaii Telescope. Despite an age of only 2Myr and a similarity with prototypical classical T Tauri stars, LkCa4 shows no evidence for accretion and probes an interesting transition stage for star and planet formation. Large profile distortions and Zeeman signatures are detected in the unpolarized and circularly-polarized lines of LkCa4 using Least-Squares Deconvolution (LSD), indicating the presence of brightness inhomogeneities and magnetic fields at the surface of LkCa4. Using tomographic imaging, we reconstruct brightness and magnetic maps of LkCa4 from sets of unpolarized and circularly-polarized LSD profiles. The large-scale field is strong and mainly axisymmetric, featuring a ~2kG poloidal component and a ~1kG toroidal component encircling the star at equatorial latitudes - the latter making LkCa4 markedly different from classical TTauri stars of similar mass and age. The brightness map includes a dark spot overlapping the magnetic pole and a bright region at mid latitudes - providing a good match to the contemporaneous photometry. We also find that differential rotation at the surface of LkCa4 is small, typically ~5.5x weaker than that of the Sun, and compatible with solid-body rotation. Using our tomographic modelling, we are able to filter out the activity jitter in the RV curve of LkCa4 (of full amplitude 4.3km/s) down to a rms precision of 0.055km/s. Looking for hot Jupiters around young Sun-like stars thus appears feasible, even though we find no evidence for such planets around LkCa4., Comment: MNRAS in press (11 pages, 8 figures, 2 tables)

Published
2017
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76. Investigating the magnetospheric accretion process in the young pre-transitional disk system DoAr 44 (V2062 Oph): A multiwavelength interferometric, spectropolarimetric, and photometric observing campaign.

Author

Bouvier, J., Alecian, E., Alencar, S. H. P., Sousa, A., Donati, J.-F., Perraut, K., Bayo, A., Rebull, L. M., Dougados, C., Duvert, G., Berger, J.-P., Benisty, M., Pouilly, K., Folsom, C., and Moutou, C.

Subjects
STARSPOTS, STELLAR rotation, ACCRETION disks, LIGHT curves, ORIGIN of planets, OPTICAL spectra, PROTOPLANETARY disks, STELLAR magnetic fields
Abstract

Context. Young stars interact with their accretion disk through their strong magnetosphere. Aims. We aim to investigate the magnetospheric accretion/ejection process in the young stellar system DoAr 44 (V2062 Oph). Methods. We monitored the system over several rotational cycles, combining high-resolution spectropolarimetry at both optical and near-IR wavelengths with long-baseline near-IR inteferometry and multicolor photometry. Results. We derive a rotational period of 2.96 d from the system's light curve, which is dominated by stellar spots. We fully characterize the central star's properties from the high signal-to-noise, high-resolution optical spectra we obtained during the campaign. DoAr 44 is a young 1.2 M⊙ star, moderately accreting from its disk (Ṁacc = 6.5 10−9M⊙ yr−1), and seen at a low inclination (i ≃ 30°). Several optical and near-IR line profiles probing the accretion funnel flows (Hα, Hβ, HeI 1083 nm, Paβ) and the accretion shock (HeI 587.6 nm) are modulated at the stellar rotation period. The most variable line profile is HeI 1083 nm, which exhibits modulated redshifted wings that are a signature of accretion funnel flows, as well as deep blueshifted absorptions indicative of transient outflows. The Zeeman-Doppler analysis suggests the star hosts a mainly dipolar magnetic field, inclined by about 20° onto the spin axis, with an intensity reaching about 800 G at the photosphere, and up to 2 ± 0.8 kG close to the accretion shock. The magnetic field appears strong enough to disrupt the inner disk close to the corotation radius, at a distance of about 4.6 R⋆ (0.043 au), which is consistent with the 5 R⋆ (0.047 au) upper limit we derived for the size of the magnetosphere in our Paper I from long baseline interferometry. Conclusions. DoAr 44 is a pre-transitional disk system, exhibiting a 25–30 au gap in its circumstellar disk, with the inner and outer disks being misaligned. On a scale of 0.1 au or less, our results indicate that the system is steadily accreting from its inner disk through its tilted dipolar magnetosphere. We conclude that in spite of a highly structured disk on the large scale, perhaps the signature of ongoing planetary formation, the magnetospheric accretion process proceeds unimpeded at the star-disk interaction level. [ABSTRACT FROM AUTHOR]

Published
2020
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77. The magnetosphere of the close accreting PMS binary V4046 Sgr AB

Author

Gregory, S. G., Holzwarth, V. R., Donati, J.-F, Hussain, G. A. J., Montmerle, T., Alecian, E., Alencar, S. H. P., Argiroffi, C., Audard, M., Bouvier, J., Damiani, F., Güdel, M., Huenemoerder, D. P., Kastner, J. H., Maggio, A., Sacco, G. G., Wade, G. A., Gregory, S. G., Holzwarth, V. R., Donati, J.-F, Hussain, G. A. J., Montmerle, T., Alecian, E., Alencar, S. H. P., Argiroffi, C., Audard, M., Bouvier, J., Damiani, F., Güdel, M., Huenemoerder, D. P., Kastner, J. H., Maggio, A., Sacco, G. G., and Wade, G. A.

Abstract

We present a preliminary 3D potential field extrapolation model of the joint magnetosphere of the close accreting PMS binary V4046 Sgr. The model is derived from magnetic maps obtained as part of a coordinated optical and X-ray observing program

Published
2017

78. The close classical T Tauri binary V4046 Sgr: complex magnetic fields and distributed mass accretion

Author

Donati, J.-F, Gregory, S. G., Montmerle, T., Maggio, A., Argiroffi, C., Sacco, G., Hussain, G., Kastner, J., Alencar, S. H. P., Audard, M., Bouvier, J., Damiani, F., Güdel, M., Huenemoerder, D., Wade, G. A., Donati, J.-F, Gregory, S. G., Montmerle, T., Maggio, A., Argiroffi, C., Sacco, G., Hussain, G., Kastner, J., Alencar, S. H. P., Audard, M., Bouvier, J., Damiani, F., Güdel, M., Huenemoerder, D., and Wade, G. A.

Abstract

We report here the first results of a multi-wavelength campaign focusing on magnetospheric accretion processes within the close binary system V4046 Sgr, hosting two partly convective classical T Tauri stars of masses ≃0.9 M⊙ and age ≃12 Myr. In this paper, we present time-resolved spectropolarimetric observations collected in 2009 September with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT) and covering a full span of 7 d or ≃2.5 orbital/rotational cycles of V4046 Sgr. Small circularly polarized Zeeman signatures are detected in the photospheric absorption lines but not in the accretion-powered emission lines of V4046 Sgr, thereby demonstrating that both system components host large-scale magnetic fields weaker and more complex than those of younger, fully convective classical T Tauri stars (cTTSs) of only a few Myr and similar masses. Applying our tomographic imaging tools to the collected data set, we reconstruct maps of the large-scale magnetic field, photospheric brightness and accretion-powered emission at the surfaces of both stars of V4046 Sgr. We find that these fields include significant toroidal components, and that their poloidal components are mostly non-axisymmetric with a dipolar component of 50-100 G strongly tilted with respect to the rotation axis; given the similarity with fields of partly convective main-sequence stars of similar masses and rotation periods, we conclude that these fields are most likely generated by dynamo processes. We also find that both stars in the system show cool spots close to the pole and extended regions of low-contrast, accretion-powered emission; it suggests that mass accretion is likely distributed rather than confined in well-defined high-contrast accretion spots, in agreement with the derived magnetic field complexity

Published
2017

79. Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau

Author

Donati, J.-F, Hébrard, E., Hussain, G. A. J., Moutou, C., Malo, L., Grankin, K., Vidotto, A. A., Alencar, S. H. P., Gregory, S. G., Jardine, M. M., Herczeg, G., Morin, J., Fares, R., Ménard, F., Bouvier, J., Delfosse, X., Doyon, R., Takami, M., Figueira, P., Petit, P., Boisse, I., Donati, J.-F, Hébrard, E., Hussain, G. A. J., Moutou, C., Malo, L., Grankin, K., Vidotto, A. A., Alencar, S. H. P., Gregory, S. G., Jardine, M. M., Herczeg, G., Morin, J., Fares, R., Ménard, F., Bouvier, J., Delfosse, X., Doyon, R., Takami, M., Figueira, P., Petit, P., and Boisse, I.

Abstract

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819 Tau and V830 Tau within the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ≃3Myr, both stars dissipated their discs recently and are interesting objects for probing star and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magnetic maps for both stars. We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximated at large radii by 350-400G dipoles tilted at ≃30° to the rotation axis. They are significantly weaker than the field of GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both stars include cool spots and warm plages. Surface differential rotation is small, typically ≃4.4times smaller than on the Sun, in agreement with previous results on wTTSs. Using our Doppler images to model the activity jitter and filter it out from the radial velocity (RV) curves, we obtain RV residuals with dispersions of 0.033 and 0.104kms−1 for V819 Tau and V830 Tau, respectively. RV residuals suggest that a hot Jupiter may be orbiting V830 Tau, though additional data are needed to confirm this preliminary result. We find no evidence for close-in giant planet around V819 Tau

Published
2017

80. Modelling the magnetic activity and filtering radial velocity curves of young Suns: the weak-line T Tauri star LkCa 4

Author

Donati, J.-F, Hébrard, E., Hussain, G., Moutou, C., Grankin, K., Boisse, I., Morin, J., Gregory, S. G., Vidotto, A. A., Bouvier, J., Alencar, S. H. P., Delfosse, X., Doyon, R., Takami, M., Jardine, M. M., Fares, R., Cameron, A. C., Ménard, F., Dougados, C., Herczeg, G., Donati, J.-F, Hébrard, E., Hussain, G., Moutou, C., Grankin, K., Boisse, I., Morin, J., Gregory, S. G., Vidotto, A. A., Bouvier, J., Alencar, S. H. P., Delfosse, X., Doyon, R., Takami, M., Jardine, M. M., Fares, R., Cameron, A. C., Ménard, F., Dougados, C., and Herczeg, G.

Abstract

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa 4 within the Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets (MaTYSSE) programme, involving ESPaDOnS at the Canada-France-Hawaii Telescope. Despite an age of only 2Myr and a similarity with prototypical classical T Tauri stars, LkCa 4 shows no evidence for accretion and probes an interesting transition stage for star and planet formation. Large profile distortions and Zeeman signatures are detected in the unpolarized and circularly polarized lines of LkCa 4 using Least-Squares Deconvolution (LSD), indicating the presence of brightness inhomogeneities and magnetic fields at the surface of LkCa 4. Using tomographic imaging, we reconstruct brightness and magnetic maps of LkCa 4 from sets of unpolarized and circularly polarized LSD profiles. The large-scale field is strong and mainly axisymmetric, featuring a ≃2 kG poloidal component and a ≃1 kG toroidal component encircling the star at equatorial latitudes - the latter making LkCa4 markedly different from classical T Tauri stars of similar mass and age. The brightness map includes a dark spot overlapping the magnetic pole and a bright region at mid-latitudes - providing a good match to the contemporaneous photometry. We also find that differential rotation at the surface of LkCa 4 is small, typically ≃5.5times weaker than that of the Sun, and compatible with solid-body rotation. Using our tomographic modelling, we are able to filter out the activity jitter in the radial velocity curve of LkCa 4 (of full amplitude 4.3kms−1) down to an rms precision of 0.055kms−1. Looking for hot Jupiters around young Sun-like stars thus appears feasible, even though we find no evidence for such planets around LkCa 4

Published
2017

81. The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264

Author

Venuti, L., primary, Prisinzano, L., additional, Sacco, G. G., additional, Flaccomio, E., additional, Bonito, R., additional, Damiani, F., additional, Micela, G., additional, Guarcello, M. G., additional, Randich, S., additional, Stauffer, J. R., additional, Cody, A. M., additional, Jeffries, R. D., additional, Alencar, S. H. P., additional, Alfaro, E. J., additional, Lanzafame, A. C., additional, Pancino, E., additional, Bayo, A., additional, Carraro, G., additional, Costado, M. T., additional, Frasca, A., additional, Jofré, P., additional, Morbidelli, L., additional, Sousa, S. G., additional, and Zaggia, S., additional

Published
2017
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86. CoRoT 223992193: Investigating the variability in a low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

Author

Gillen, E., primary, Aigrain, S., additional, Terquem, C., additional, Bouvier, J., additional, Alencar, S. H. P., additional, Gandolfi, D., additional, Stauffer, J., additional, Cody, A., additional, Venuti, L., additional, Almeida, P. Viana, additional, Micela, G., additional, Favata, F., additional, and Deeg, H. J., additional

Published
2017
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87. CIRCUMSTELLAR ACTIVITY OF THE HERBIG AE STAR HD163296

Author

Pogodin, M. A., Guimaraes, M. M., Alencar, S. H. P., Corradi, W. J. B., and Vieira, S. L. A.

Subjects
lcsh:QB1-991, Stars, pre-main sequence, circumstellar matter, stars, individual, HD163296, lcsh:Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We present new results of a high-resolution spectroscopic investigation of the young Ae Herbig star HD163296. Nineteen spectra of this object had been obtained on May 8 - 10, 2002 at the ESO with the FEROS echelle spectrometer installed at the 1.52m telescope. Striking profile variability has been found in a number of lines originating in the stellar wind. Analysis of the variability revealed manifestation of a layered spatial structure of the wind zone containing layers of preferable generation of local inhomogeneities in the outflowing gas. Correlation between different spectral parameters corresponding to infall and outflow gaseous streams evidence in favour of the physical interdependence between the accretion and the mass loss processes in the circumstellar envelope.

Published
2007

88. Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau

Author

Donati, J. -F., Hébrard, E., Hussain, G. A. J., Moutou, C., Malo, L., Grankin, K., Vidotto, A. A., Alencar, S. H. P., Gregory, S. G., Jardine, M. M., Herczeg, G., Morin, J., Fares, R., Ménard, F., Bouvier, J., Delfosse, X., Doyon, R., Takami, M., Figueira, P., Petit, P., Boisse, I., Collaboration, MaTYSSE, 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), University of St Andrews [Scotland], Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Crimean Astrophysical Observatory (CrAO), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Universidade Federal de Minas Gerais [Belo Horizonte] (UFMG), Kavli Institute for Astronomy and Astrophysics [Beijing] (KIAA-PKU), Peking University [Beijing], Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université de Montréal (UdeM), Academia Sinica, Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto [Porto], 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), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Universidade do Porto, Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy, 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), Université de Genève = University of Geneva (UNIGE), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Universidade do Porto = University of Porto, 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
magnetic fields [Stars], NDAS, FOS: Physical sciences, individual: V830 Tau [Stars], Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, polarimetric [Techniques], 01 natural sciences, Planet, 0103 physical sciences, Hot Jupiter, QB Astronomy, Differential rotation, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), formation [Stars], Astrophysics::Galaxy Astrophysics, QB, Physics, 010308 nuclear & particles physics, Giant planet, Astronomy, Astronomy and Astrophysics, Exoplanet, Radial velocity, Stars, T Tauri star, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, imaging [Stars], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], individual: V819 Tau [Stars]
Abstract

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819 Tau and V830 Tau within the MaTYSSE programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ~3 Myr, both stars dissipated their discs recently and are interesting objects for probing star and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly-polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magnetic maps for both stars. We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximated at large radii by 350-400 G dipoles tilted at ~30 degrees to the rotation axis. They are significantly weaker than the field of GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both stars include cool spots and warm plages. Surface differential rotation is small, typically ~4.4x smaller than on the Sun, in agreement with previous results on wTTSs. Using our Doppler images to model the activity jitter and filter it out from the radial velocity (RV) curves, we obtain RV residuals with dispersions of 0.033 and 0.104 km/s for V819 Tau and V830 Tau respectively. RV residuals suggest that a hot Jupiter may be orbiting V830 Tau, though additional data are needed to confirm this preliminary result. We find no evidence for close-in giant planet around V819 Tau., MNRAS in press (15 pages, 12 figures, 3 tables)

Published
2015
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89. Magnetic topologies of young suns: the weak-line T Tauri stars TWA 6 and TWA 8A.

Author

Hill, C A, Folsom, C P, Donati, J-F, Herczeg, G J, Hussain, G A J, Alencar, S H P, and Gregory, S G

Subjects
MAGNETIC flux density, EARLY stars, GAS giants, STARS
Abstract

We present a spectropolarimetric study of two weak-line T Tauri stars (wTTSs), TWA 6, and TWA 8A, as part of the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme. Both stars display significant Zeeman signatures that we have modelled using Zeeman Doppler Imaging (ZDI). The magnetic field of TWA 6 is split equally between poloidal and toroidal components, with the largest fraction of energy in higher order modes, with a total unsigned flux of 840 G, and a poloidal component tilted 35° from the rotation axis. TWA 8A has a 70 per cent poloidal field, with most of the energy in higher order modes, with an unsigned flux of 1.4 kG (with a magnetic filling factor of 0.2), and a poloidal field tilted 20° from the rotation axis. Spectral fitting of the very strong field in TWA 8A (in individual lines, simultaneously for Stokes I and V) yielded a mean magnetic field strength of 6.0 ± 0.5 kG. The higher field strengths recovered from spectral fitting suggests that a significant proportion of magnetic energy lies in small-scale fields that are unresolved by ZDI. So far, wTTSs in MaTYSSE appear to show that the poloidal-field axisymmetry correlates with the magnetic field strength. Moreover, it appears that classical T Tauri stars (cTTSs) and wTTSs are mostly poloidal and axisymmetric when mostly convective and cooler than ∼4300 K, with hotter stars being less axisymmetric and poloidal, regardless of internal structure. [ABSTRACT FROM AUTHOR]

Published
2019
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92. CSI 2264: Accretion process in classical T Tauri stars in the young cluster NGC 2264

Author

Sousa, A. P., primary, Alencar, S. H. P., additional, Bouvier, J., additional, Stauffer, J., additional, Venuti, L., additional, Hillenbrand, L., additional, Cody, A. M., additional, Teixeira, P. S., additional, Guimarães, M. M., additional, McGinnis, P. T., additional, Rebull, L., additional, Flaccomio, E., additional, Fürész, G., additional, Micela, G., additional, and Gameiro, J. F., additional

Published
2016
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93. The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264.

Author

Venuti, L., Prisinzano, L., Sacco, G. G., Flaccomio, E., Bonito, R., Damiani, F., Micela, G., Guarcello, M. G., Randich, S., Stauffer, J. R., Cody, A. M., Jeffries, R. D., Alencar, S. H. P., Alfaro, E. J., Lanzafame, A. C., Pancino, E., Bayo, A., Carraro, G., Costado, M. T., and Frasca, A.

Subjects
STAR clusters, ORIGIN of planets, STELLAR evolution, DISKS (Astrophysics), STELLAR structure, STAR formation
Abstract

Context. Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. Aims. We aim to explore the structure of the open cluster and star-forming region NGC 2264 (~3 Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. Methods. We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8 M☉ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g; r; i photometry from CSI 2264 to derive individual extinction and stellar parameters. Results. We find a significant age spread of 4-5 Myr among cluster members. Disk-bearing objects are statistically associated with younger isochronal ages than disk-free sources. The cluster has a hierarchical structure, with two main blocks along its latitudinal extension. The northern half develops around the O-type binary star S Mon; the southern half, close to the tip of the Cone Nebula, contains the most embedded regions of NGC 2264, populated mainly by objects with disks and ongoing accretion. The median ages of objects at di erent locations within the cluster, and the spatial distribution of disked and non-disked sources, suggest that star formation began in the north of the cluster, over 5 Myr ago, and was ignited in its southern region a few Myr later. Star formation is likely still ongoing in the most embedded regions of the cluster, while the outer regions host a widespread population of more evolved objects; these may be the result of an earlier star formation episode followed by outward migration on timescales of a few Myr. We find a detectable lag between the typical age of disk-bearing objects and that of accreting objects in the inner regions of NGC 2264: the first tend to be older than the second, but younger than disk-free sources at similar locations within the cluster. This supports earlier findings that the characteristic timescales of disk accretion are shorter than those of disk dispersal, and smaller than the average age of NGC 2264 (i.e., ≲3 Myr). At the same time, we note that disks in the north of the cluster tend to be shorter-lived (~2.5 Myr) than elsewhere; this may reflect the impact of massive stars within the region (notably S Mon), that trigger rapid disk dispersal. Conclusions. Our results, consistent with earlier studies on NGC 2264 and other young clusters, support the idea of a star formation process that takes place sequentially over a prolonged span in a given region. A complete understanding of the dynamics of formation and evolution of star clusters requires accurate astrometric and kinematic characterization of its population; significant advance in this field is foreseen in the upcoming years thanks to the ongoing Gaia mission, coupled with extensive ground-based surveys like GES. [ABSTRACT FROM AUTHOR]

Published
2018
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94. Magnetometry of the classical T Tauri star GQ Lup: non-stationary dynamos and spin evolution of young Suns

Author

Donati, J. F., Gregory, S. G., Alencar, S. H. P., Hussain, G., Bouvier, J., Dougados, C., Jardine, M. M., Menard, F., Romanova, M. M., Collaboration, the MaPP, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
techniques: polarimetric, stars: formation, Astrophysics - Solar and Stellar Astrophysics, stars: rotation, [SDU]Sciences of the Universe [physics], stars: magnetic field, stars: individual: GQ Lup, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, stars: imaging, Astrophysics::Galaxy Astrophysics
Abstract

We report here results of spectropolarimetric observations of the classical T Tauri star (cTTS) GQ Lup carried out with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT) in the framework of the "Magnetic Protostars and Planets" (MaPP) programme, and obtained at 2 different epochs (2009 July & 2011 June). From these observations, we first infer that GQ Lup has a photospheric temperature of 4,300+-50\^A K and a rotation period of 8.4+-0.3 d; it implies that it is a 1.05+-0.07 Msun star viewed at an inclination of ~30deg, with an age of 2-5 Myr, a radius of 1.7+-0.2 Rsun, and has just started to develop a radiative core. Large Zeeman signatures are clearly detected at all times, both in photospheric lines & in accretion-powered emission lines, probing longitudinal fields of up to 6 kG and hence making GQ Lup the cTTS with the strongest large-scale fields known as of today. Rotational modulation of Zeeman signatures is clearly different between our 2 runs, demonstrating that large-scale fields of cTTSs are evolving with time and are likely produced by non-stationary dynamo processes. Using tomographic imaging, we reconstruct maps of the large-scale field, of the photospheric brightness & of the accretion-powered emission of GQ Lup. We find that the magnetic topology is mostly poloidal & axisymmetric; moreover, the octupolar component of the large-scale field (of strength 2.4 & 1.6 kG in 2009 & 2011) dominates the dipolar component (of strength ~1 kG) by a factor of ~2, consistent with the fact that GQ Lup is no longer fully-convective. GQ Lup also features dominantly poleward magnetospheric accretion at both epochs. The large-scale dipole of GQ Lup is however not strong enough to disrupt the surrounding accretion disc further than about half-way to the corotation radius, suggesting that GQ Lup should rapidly spin up like other similar partly-convective cTTSs (abridged)., Comment: MNRAS, in press (17 pages, 10 figures, 1 table)

Published
2012
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95. The close classical T Tauri binary V4046 Sgr: Complex magnetic fields & distributed mass accretion

Author

Donati, J.-F, Gregory, S. G., Montmerle, T., Maggio, A., Argiroffi, C., Sacco, G., Hussain, G., Kastner, J., Alencar, S. H. P., Audard, M., Bouvier, J., Damiani, F., Güdel, M., Huenemoerder, D., Wade, G. A., Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Donati, JF, Gregory, SG, Montmerle, T, Maggio, A, Argiroffi, C, Sacco, G, Hussain, G, Kastner, J, Alencar, SHP, Audard, M, Bouvier, J, Damiani, F, Güdel, M, Huenemoerder, D, and Wade, GA

Subjects
stars: formation, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], stars: individual: V4046 Sgr, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: imaging, techniques: polarimetric, Settore FIS/05 - Astronomia E Astrofisica, Astrophysics - Solar and Stellar Astrophysics, stars: rotation, [SDU]Sciences of the Universe [physics], stars: magnetic fields, Astrophysics::Solar and Stellar Astrophysics, techniques: polarimetric, stars: formation, stars: imaging, stars: individual: V4046 Sgr, stars: magnetic fields, stars: rotation, Astrophysics::Earth and Planetary Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract

We report here the first results of a multi-wavelength campaign focussing on magnetospheric accretion processes within the close binary system V4046 Sgr, hosting two partly-convective classical T Tauri stars of masses ~0.9 Msun and age ~12 Myr. In this paper, we present time-resolved spectropolarimetric observations collected in 2009 September with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT) and covering a full span of 7d or ~2.5 orbital/rotational cycles of V4046 Sgr. Small circularly polarised Zeeman signatures are detected in the photospheric absorption lines but not in the accretion-powered emission lines of V4046 Sgr, thereby demonstrating that both system components host large-scale magnetic fields weaker and more complex than those of younger, fully-convective cTTSs of only a few Myr and similar masses. Applying our tomographic imaging tools to the collected data set, we reconstruct maps of the large-scale magnetic field, photospheric brightness and accretion-powered emission at the surfaces of both stars of V4046 Sgr. We find that these fields include significant toroidal components, and that their poloidal components are mostly non-axisymmetric with a dipolar component of 50-100G strongly tilted with respect to the rotation axis; given the similarity with fields of partly-convective main-sequence stars of similar masses and rotation periods, we conclude that these fields are most likely generated by dynamo processes. We also find that both stars in the system show cool spots close to the pole and extended regions of low-contrast, accretion-powered emission; it suggests that mass accretion is likely distributed rather than confined in well defined high-contrast accretion spots, in agreement with the derived magnetic field complexity., MNRAS in press (13 pages, 7 figures)

Published
2011
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97. CSI 2264: Probing the inner disks of AA Tauri-like systems in NGC 2264

Author

McGinnis, P. T., primary, Alencar, S. H. P., additional, Guimarães, M. M., additional, Sousa, A. P., additional, Stauffer, J., additional, Bouvier, J., additional, Rebull, L., additional, Fonseca, N. N. J., additional, Venuti, L., additional, Hillenbrand, L., additional, Cody, A. M., additional, Teixeira, P. S., additional, Aigrain, S., additional, Favata, F., additional, Fűrész, G., additional, Vrba, F. J., additional, Flaccomio, E., additional, Turner, N. J., additional, Gameiro, J. F., additional, Dougados, C., additional, Herbst, W., additional, Morales-Calderón, M., additional, and Micela, G., additional

Published
2015
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98. Accretion dynamics and disk evolution in NGC 2264: a study based on CoRoT photometric observations

Author

Alencar, S. H. P., Teixeira, P. S., Guimarães, M. M., Mcginnis, P. T., Gameiro, J. F., Bouvier, J., Aigrain, S., Flaccomio, E., Favata, F., Laboratoire d'Astrophysique de Grenoble (LAOG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]
Abstract

International audience; Context. The young cluster NGC 2264 was observed with the CoRoT satellite for 23 days uninterruptedly in March 2008 withunprecedented photometric accuracy. We present the first results of our analysis of the accreting population belonging to the clusteras observed by CoRoT.Aims. We search for possible light curve variability of the same nature as that observed in the classical T Tauri star AA Tau, whichwas attributed to a magnetically controlled inner disk warp. The inner warp dynamics is supposed to be directly associated with theinteraction between the stellar magnetic field and the inner disk region.Methods. We analyzed the CoRoT light curves of 83 previously known classical T Tauri stars that belong to NGC 2264 classifyingthem according to their light-curve morphology. We also studied the CoRoT light-curve morphology as a function of a Spitzer-basedclassification of the star-disk systems.Results. The classification derived on the basis of the CoRoT light-curve morphology agrees very well with the Spitzer IRAC-basedclassification of the systems. The percentage of AA Tau-like light curves decreases as the inner disk dissipates, from 40% ±10%in systems with thick inner disks to 36% ±16% in systems with anemic disks and zero in naked photosphere systems. Indeed,91% ±29% of the CTTS with naked photospheres exhibit pure spot-like variability, while only 18% ±7% of the thick disk systemsdo so, presumably those seen at low inclination and thus free of variable obscuration.Conclusions. AA Tau-like light curves are found to be fairly common, with a frequency of at least ∼30 to 40% in young starswith inner dusty disks. The temporal evolution of the light curves indicates that the structure of the inner disk warp, located close tothe corotation radius and responsible for the obscuration episodes, varies over a timescale of a few (∼1–3) rotational periods. This probably reflects the highly dynamical nature of the star-disk magnetospheric interaction.

Published
2010

99. The hot Jupiter of the magnetically active weak-line T Tauri star V830 Tau.

Author

Donati, J. -F., Yu, L., Moutou, C., Cameron, A. C., Malo, L., Grankin, K., Hébrard, E., Hussain, G. A. J., Vidotto, A. A., Alencar, S. H. P., Haywood, R. D., Bouvier, J., Petit, P., Takami, M., Herczeg, G. J., Gregory, S. G., Jardine, M. M., and Morin, J.

Subjects
HOT Jupiters, T Tauri stars, ASTROPHYSICAL spectropolarimetry, ASTRONOMICAL photometry, STAR observations
Abstract

We report results of an extended spectropolarimetric and photometric monitoring of the weakline T Tauri star V830 Tau and its recently detected newborn close-in giant planet. Our observations, carried out within the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme, were spread over 91 d, and involved the ESPaDOnS and Narval spectropolarimeters linked to the 3.6-m Canada-France-Hawaii, the 2-m Bernard Lyot, and the 8-m Gemini-North Telescopes. Using Zeeman-Doppler Imaging, we characterize the surface brightness distributions, magnetic topologies, and surface differential rotation of V830 Tau at the time of our observations, and demonstrate that both distributions evolve with time beyond what is expected from differential rotation. We also report that near the end of our observations, V830 Tau triggered one major flare and two weaker precursors, showing up as enhanced redshifted emission in multiple spectral activity proxies. With three different filtering techniques, we model the radial velocity (RV) activity jitter (of semi-amplitude 1.2 km s-1) that V830 Tau generates, successfully retrieve the 68 ± 11 m s-1 RV planet signal hiding behind the jitter, further confirm the existence of V830 Tau b, and better characterize its orbital parameters. We find that the method based on Gaussian-process regression performs best thanks to its higher ability at modelling not only the activity jitter, but also its temporal evolution over the course of our observations, and succeeds at reproducing our RV data down to an rms precision of 35 m s-1. Our result provides new observational constraints on scenarios of star/planet formation and demonstrates the scientific potential of large-scale searches for close-in giant planets around T Tauri stars. [ABSTRACT FROM AUTHOR]

Published
2017
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