New Stellar Parameters, Metallicities, and Elemental Abundance Ratios for 311 Metal-poor Stars

Abstract

We present equivalent widths, improved model atmosphere parameters, and revised abundances for 14 species of 11 elements derived from high-resolution optical spectroscopy of 311 metal-poor stars. All of these stars had their parameters previously published by Roederer et al. We use color– T _eff relationships calibrated for Gaia and 2MASS photometry to calculate improved effective temperatures ( T _eff ). We calculate log of surface gravity (log g ) values using measurements derived from Gaia parallaxes and other fundamental stellar properties. We perform a standard LTE abundance analysis using MARCS model atmospheres and the MOOG line analysis software to rederive microturbulence velocity parameters, metallicities, and abundances based on O i , Na i , Mg i , Si i , K i , Ca i , Ti i , Ti ii , Cr i , Cr ii , Fe i , Fe ii , Ni i , and Zn i lines using previously measured equivalent widths. On average, the new T _eff values are 310 K warmer, the new log g values are higher by 0.64 dex, and the new [Fe/H] values are higher by 0.26 dex. We apply NLTE corrections to the abundances derived from O i , Na i , Mg i , Si i , K i , Fe i , and Fe ii lines. Our sample contains 6 stars with [Fe/H] < −3.5, 28 stars with [Fe/H] < −3.0, and 113 stars with [Fe/H] < −2.5. Our revised abundances for these 311 stars are now in better agreement with those derived by previous studies of smaller samples of metal-poor stars in the Milky Way.

Keywords

• Nucleosynthesis
• Population II stars
• Stellar abundances
• Stellar astronomy