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

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.

In: Monthly Notices of the Royal Astronomical Society, 2014, vol. 444, no. 4, p. 3220-3229

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    Titel
    • Modelling the magnetic activity and filtering radial velocity curves of young Suns
      the weak-line T Tauri star LkCa 4
    Autor
    • Donati, J.-F. Université de Toulouse / CNRS-INSU, IRAP / UMR 5277, F-31400 Toulouse, France
    • Hébrard, E.. Université de Toulouse / CNRS-INSU, IRAP / UMR 5277, F-31400 Toulouse, France
    • Hussain, G.. Université de Toulouse / CNRS-INSU, IRAP / UMR 5277, F-31400 Toulouse, France
    • Moutou, C.. CFHT Corporation, 65-1238 Mamalahoa Hwy, Kamuela, Hawaii 96743, USA
    • Grankin, K.. Crimean Astrophysical Observatory, Nauchny, Crimea 298409, Russia
    • Boisse, I.. Université Aix-Marseille / CNRS-INSU, LAM / UMR 7326, F-13388 Marseille, France
    • Morin, J.. Université Montpellier / CNRS-INSU, LUPM / UMR 5299, F-34095 Montpellier, France
    • Gregory, S. G.. School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
    • Vidotto, A. A.. Observatoire de Genève, Chemin des Maillettes 51, CH-1290 Versoix, Switzerland
    • Bouvier, J.. Université Joseph Fourier / CNRS-INSU, IPAG / UMR 5274, F-38041 Grenoble, France
    • Alencar, S. H. P.. Departamento de Fìsica - ICEx - UFMG, Av. Antônio Carlos, 6627, 30270-901 Belo Horizonte, MG, Brazil
    • Delfosse, X.. Université Joseph Fourier / CNRS-INSU, IPAG / UMR 5274, F-38041 Grenoble, France
    • Doyon, R.. Département de physique, Université de Montr'eal, C.P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7, Canada
    • Takami, M.. Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 106, Taipei, Taiwan
    • Jardine, M. M.. School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
    • Fares, R.. School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
    • Cameron, A. C.. School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
    • Ménard, F.. UMI-FCA, CNRS/INSU, France (UMI 3386), and Universidad de Chile, 1058 Santiago, Chile
    • Dougados, C.. Université Joseph Fourier / CNRS-INSU, IPAG / UMR 5274, F-38041 Grenoble, France
    • Herczeg, G.. Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871, China
    Dokumententyp
    • Postprint
    Sprache
    • Englisch
    Veröffentlicht in
    • Monthly Notices of the Royal Astronomical Society, 2014, vol. 444, no. 4, p. 3220-3229. Oxford University Press
    Andere elektronische Ausgabe
    OAI-PMH-ID
    • oai:doc.rero.ch:301055
    Summary
    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