Abundances in the Local Region I: G and K Giants

TL;DR

This study analyzes 1133 G and K giant stars to determine their parameters and abundances, revealing issues with gravity measurements and supporting standard stellar evolution models through observed abundance patterns.

Contribution

It provides a large-scale analysis of stellar parameters and abundances, highlighting the discrepancy in gravity determinations and confirming mass-dependent mixing in giants.

Findings

Giants have Sun-like total abundances and ratios.

Ionization balance gravity is preferred over isochrone-derived gravity.

Evidence of mass-dependent mixing consistent with stellar evolution models.

Abstract

Parameters and abundances for 1133 stars of spectral types F, G, and K of luminosity class III have been derived. In terms of stellar parameters, the primary point of interest is the disagreement between gravities derived with masses determined from isochrones, and gravities determined from an ionization balance. This is not a new result per se; but the size of this sample emphasizes the severity of the problem. A variety of arguments lead to the selection of the ionization balance gravity as the working value. The derived abundances indicate that the giants in the solar region have Sun-like total abundances and abundance ratios. Stellar evolution indicators have also been investigated with the Li abundances and the [C/Fe] and C/O ratios indicating that standard processing has been operating in these stars. The more salient result for stellar evolution is that the [C/Fe] data across the red-giant clump indicates the presence of mass dependent mixing in accord with standard stellar evolution predictions. Keywords: stars: fundamental parameters - stars: abundances - stars: evolution - Galaxy: abundances