Stellar Parameters

A fundamental aspect of the construction of stellar population models is the set of stellar parameters adopted for the library stars. Here we provide a brief summary of our method to determine the effective temperatures ($T_{\rm eff}$), iron abundances ([Fe/H]) and surface gravities ($\log g$) of F and G dwarfs, and G and K giants. A more detailed description can be found in Paper I. Since the main focus of that paper was reproducing the observations of a mildly metal-rich Galactic globular cluster (47 Tuc), we did not provide a detailed account of our procedure to determine the stellar parameters of stars outside the above range of spectra types. Therefore, we briefly summarize here the determination of stellar parameters for FG dwarfs and GK giants, and in the following subsections we describe the determinations for cooler and hotter stars.

For dwarf stars, $T_{\rm eff}$ and [Fe/H] were estimated from Strömgren photometry adopting the calibrations by Alonso et al. (1996) and Schuster & Nissen (1989, as revised by Clementini et al. 1999). For giants those parameters are based on the $T_{\rm eff}$ and [Fe/H] scales of Soubiran, Katz & Cayrel (1998), through the construction of a relation between absorption line features and stellar parameters for a sub-sample of the library stars in common with that study (see details in Paper I). For all the stars, $\log g$ was determined using Hipparcos parallaxes, bolometric corrections inferred from the calibrations by Alonso et al. (1995, 1999) and an assumed mass. A discussion of the uncertainties in these stellar parameter determinations can be found in Paper I.