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Issue A&A
Volume 457, Number 1, October I 2006
Page(s) L9 - L12
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20065917



A&A 457, L9-L12 (2006)
DOI: 10.1051/0004-6361:20065917

Letter

Accurate stellar masses in the multiple system T Tauri

G. Duchêne1, H. Beust1, F. Adjali1, Q. M. Konopacky2 and A. M. Ghez2

1  Laboratoire d'Astrophysique de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
    e-mail: gaspard.duchene@obs.ujf-grenoble.fr
2  Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1562, USA

(Received 27 June 2006 / Accepted 26 July 2006)

Abstract
Aims.We obtain accurate estimates for the individual masses of the components of the tight binary system T Tau S to settle the ongoing debate on the nature of T Tau Sa, a so-called infrared companion.
Methods.We take advantage of the fact that T Tau S belongs to a triple system composed of two hierarchical orbits to simultaneously analyze the motion of T Tau Sb in the rest frames of T Tau Sa and T Tau N. With this method, it is possible to pinpoint the location of the center of mass of T Tau S and, thereby, to determine individual masses for T Tau Sa and T Tau Sb with no prior assumption about the mass/flux ratio of the system. This improvement over previous studies of the system results in much better constraints on orbital parameters.
Results.We find individual masses of $2.73\pm0.31\,M_\odot$ for T Tau Sa and of $0.61\pm0.17\,M_\odot$ for T Tau Sb (in agreement with its early-M spectral type), including the uncertainty on the distance to the system. These are among the most precise estimates of the mass of any Pre-Main Sequence star, a remarkable result since this is the first system in which individual masses of T Tauri stars can be determined from astrometry only. This model-independent analysis confirms that T Tau Sa is an intermediate-mass star, presumably a very young Herbig Ae star, that may possess an almost edge-on disk.


Key words: stars: individual: T Tau -- stars: pre-main sequence -- binaries: close -- astrometry



© ESO 2006


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