Astron. Astrophys. 327, 1039-1053 (1997)

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

Abstract

We present extensive calculations of the structure and the evolution of low-mass stars in the range 0.07-0.8 , for metallicities . 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 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, 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 130.79.128.5

Contents

• 1. Introduction
• 2. Input physics
  • 2.1. The equation of state
  • 2.2. The nuclear reaction rates
  • 2.3. Deuterium-burning on the main sequence
  • 2.4. Model atmospheres
  • 2.5. Boundary conditions
• 3. Evolutionary tracks
  • 3.1. Mechanical and thermal properties
    • 3.1.1. Internal structure
    • 3.1.2. Luminosity
  • 3.2. Full convection limit
  • 3.3. Abundance of light elements
• 4. Mass-dependence of the photospheric quantities
  • 4.1. Mass-luminosity relationship
  • 4.2. Mass-effective temperature relationship
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: April 6, 1998
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