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Issue A&A
Volume 446, Number 2, February I 2006
Page(s) 635 - 641
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20053187

A&A 446, 635-641 (2006)
DOI: 10.1051/0004-6361:20053187

The limb darkening of $\mathsf{\alpha}$ Centauri B

Matching 3D hydrodynamical models with interferometric measurements
L. Bigot1, P. Kervella2, F. Thévenin1 and D. Ségransan3

1  Département Cassiopée, UMR 6202, Observatoire de la Côte d'Azur, BP 4229, 06304 Nice Cedex 4, France
    e-mail: lbigot@obs-nice.fr
2  LESIA, UMR 8109, Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
3  Observatoire de Genève, 1290 Sauverny, Switzerland

(Received 4 April 2005 / Accepted 12 September 2005)

Abstract
For the nearby dwarf star $\alpha$ Cen B (K1 V), we present limb-darkening predictions from a 3D hydrodynamical radiative transfer model of its atmosphere. We first compared the results of this model to a standard Kurucz's atmosphere. Then we used both predictions to fit the new interferometric visibility measurements of $\alpha$ Cen B obtained with the VINCI instrument of the VLT Interferometer. Part of these new visibility measurements were obtained in the second lobe of the visibility function, which is sensitive to stellar limb-darkening. The best agreement is found for the 3D atmosphere limb-darkening model and a limb-darkened angular diameter of $\theta_{\rm 3D} = 6.000\pm 0.021$ mas, corresponding to a linear radius of $0.863 \pm 0.003\,R_\odot$ (assuming $\pi = 747.1 \pm 1.2$ mas). Our new linear radius agrees well with the asteroseismic value predicted by Thévenin et al. (2002, A&A, 392, L9). In view of future observations of this star with the VLTI/AMBER instrument, we also present limb-darkening predictions in the J, H, and K bands.


Key words: instrumentation: interferometers -- stars: atmospheres

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© ESO 2006


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