Element enhancements along the entire AGB phase

TL;DR

This study provides observational data on elemental abundances in AGB stars, confirming relationships between carbon, C/O ratios, and s-process element enhancements, aiding comparison with theoretical models.

Contribution

It offers detailed abundance measurements across the AGB phase, quantifying relationships between C, C/O, and s-process element enhancements for the first time.

Findings

C/O ratios range from 0.4 to 1.0 in AGB stars.

C enhancements between 0.1 and 0.9 dex observed.

s-process element enhancements up to 1.0 dex.

Abstract

The results of a study of the AGB phase of stellar evolution are presented. Abundances have been determined for Fe, C, O, the light s-process elements, Y and Zr, the heavy s-process elements, La and Nd, and the r-process element, Eu. The expected relationship between enhanced C, increasing C/O ratio and enhanced s-process elements has been quantified. Results are presented to provide observational data with which to compare theoretical predictions. The results in this paper confirm previously suggested relationships between C, C/O and s-process element enhancements. It is seen that AGB stars show C/O ratios from C/O around 0.4 to 1.0, while C enhancements lie between [C/Fe]=0.1 to 0.9 dex. Enhancements of s-process elements are as much as [s/Fe] around 1.0 dex for the stars in which C is also greatly enhanced.