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

TL;DR

This study provides revised stellar parameters and elemental abundances for 311 metal-poor stars using high-resolution spectroscopy, improved photometric calibrations, Gaia data, and NLTE corrections, enhancing the accuracy of metal-poor star characterization.

Contribution

It introduces updated stellar parameters and abundances for a large sample of metal-poor stars using new calibration methods and Gaia data, improving upon previous measurements.

Findings

New Teff values are on average 310 K warmer.

Surface gravity log g is higher by 0.64 dex.

Metallicity [Fe/H] is higher by 0.26 dex.

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-Teff relationships calibrated for Gaia and 2MASS photometry to calculate improved effective temperatures. We calculate log of surface gravity 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 the previously measured equivalent widths. On average, the new Teff 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.