Stellar mass and age determinations

I. Grids of stellar models from Z = 0.006 to 0.04 and M = 0.5 to 3.5 M_⊙^⋆,⋆⋆

¹ Observatoire de Genève, Université de Genève, chemin des Maillettes, 1290 Versoix, Switzerland
e-mail: nami.mowlavi@unige.ch
² ISDC, Observatoire de Genève, Université de Genève, chemin d’Écogia, 1290 Versoix, Switzerland
³ Centre de Recherche Astrophysique, École Normale Supérieure de Lyon, 46 allée d’Italie, 69384 Lyon Cedex 07, France

Received: 21 July 2011
Accepted: 1 December 2011

Abstract

Aims. We present dense grids of stellar models suitable for comparison with observable quantities measured with great precision, such as those derived from binary systems or planet-hosting stars.

Methods. We computed new Geneva models without rotation at metallicities Z = 0.006, 0.01, 0.014, 0.02, 0.03, and 0.04 (i.e. [Fe/H] from −0.33 to +0.54) and with mass in small steps from 0.5 to 3.5 M_⊙. Great care was taken in the procedure for interpolating between tracks in order to compute isochrones.

Results. Several properties of our grids are presented as a function of stellar mass and metallicity. Those include surface properties in the Hertzsprung-Russell diagram, internal properties including mean stellar density, sizes of the convective cores, and global asteroseismic properties.

Conclusions. We checked our interpolation procedure and compared interpolated tracks with computed tracks. The deviations are less than 1% in radius and effective temperatures for most of the cases considered. We also checked that the present isochrones provide nice fits to four couples of observed detached binaries and to the observed sequences of the open clusters NGC 3532 and M 67. Including atomic diffusion in our models with M < 1.1 M_⊙ leads to variations in the surface abundances that should be taken into account when comparing with observational data of stars with measured metallicities. For that purpose, iso-Z_surf lines are computed. These can be requested for download from a dedicated web page, together with tracks at masses and metallicities within the limits covered by the grids. The validity of the relations linking Z and  [Fe/H]  is also re-assessed in light of the surface abundance variations in low-mass stars.