Si and Ca Abundances of a Selected Sample of Evolved Stars

Abstract

Recently we have published the detailed spectroscopic analysis of 72 evolved stars, previously studied for accurate radial velocity variations (da Silva et al. 2006). The spectroscopic observations were performed with the FEROS spectrograph (RP ∼ 50000) at the 1.5m ESO telescope at La Silla (Chile). The stellar atmosphere parameters (Teff, log g,[Fe/H]) and the micro-turbulence velocities were determined spectroscopically, using a LTE code and the MARCS models. These metallicities, together with the Teff values and the absolute V-band magnitude derived from Hipparcos parallaxes, were used to estimate basic stellar parameters (ages, masses, radii, (B-V)o and log g) using theoretical isochrones and a modified version of (2005) method. The (B-V)o values so estimated turn out to be in excellent agreement with the observed ones, confirming the reliability of the (Teff,(B-V)o) relation used in the isochrones. The estimated stellar diameters also are in good agreement, with the ones measured by independent methods, better than 0.3 mas.