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Astron. Astrophys. 327, 1039-1053

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Structure and evolution of low-mass stars*

Gilles Chabrier and Isabelle Baraffe

Centre de Recherche Astrophysique de Lyon (UMR 5574 CNRS) Ecole Normale Supérieure de Lyon, F-69364 Lyon Cedex 07, France
(e-mail: chabrier, ibaraffe @cral.ens-lyon.fr)

Received 12 November 1996 / Accepted 11 April 1997


We present extensive calculations of the structure and the evolution of low-mass stars in the range 0.07-0.8 $M_\odot$, for metallicities $-2.0\le [M/H]\le 0.0$. These calculations are based on the most recent description of the microphysics characteristic of these dense and cool objects and on the latest generation of grainless non-grey atmosphere models. We examine the evolution of the different mechanical and thermal properties of these objects as a function of mass and metallicity. We also demonstrate the inaccuracy of grey models and $T(\tau)$ relationships under these conditions. We provide detailed tables of the mass-radius-luminosity-effective temperature relations for various ages and metallicities, aimed at calibrating existing or future observations of low-mass stars and massive brown dwarfs. We derive new hydrogen-burning minimum masses, within the afore-mentioned metallicity range. These minimum masses are found to be smaller than previous estimates, a direct consequence of non-grey effects.

At last, we examine the evolution of the abundance of light elements, Li, Be and B, as a function of age, mass and metallicity.

Key words: stars: low mass, brown dwarfs - stars: abundances

*Tables 2 to 7 are only available in electronic form via the CDS at anonymous ftp

© European Southern Observatory (ESO) 1997

Online publication: October 20, 1997
Last change: April 6, 1998