Using Binary Population Synthesis to Examine the Impact of Binary Evolution on the C, N, O, and $S$-Process Yields of Solar-Metallicity Low- and Intermediate-Mass Stars

TL;DR

This paper uses binary population synthesis to study how binary interactions affect the element yields of low- and intermediate-mass stars at solar metallicity, revealing significant reductions in C and s-process element ejections and insights into Ba star abundances.

Contribution

It updates AGB star abundances in a binary synthesis model, calibrates third dredge-up, and examines binary effects on element yields, providing new insights into stellar populations and nucleosynthesis.

Findings

Binary fraction of 0.7 reduces C and s-process yields by 20-25%.

Models reproduce most Ba star abundances but overestimate high [Ce/Y] cases.

Predicts rare high-mass (>10 M_sun) Ba stars.

Abstract

Asymptotic giant branch (AGB) stars play a significant role in our understanding of the origin of the elements. They contribute to the abundances of C, N, and approximately $50\%$ of the abundances of the elements heavier than iron. An aspect often neglected in studies of AGB stars is the impact of a stellar companion on AGB stellar evolution and nucleosynthesis. In this study, we update the stellar abundances of AGB stars in the binary population synthesis code \textsc{binary\_c} and calibrate our treatment of the third dredge-up using observations of Galactic carbon stars. We model stellar populations of low- to intermediate-mass stars at solar-metallicity and examine the stellar wind contributions to C, N, O, Sr, Ba, and Pb yields at binary fractions between 0 and 1. For a stellar population with a binary fraction of 0.7, we find $\sim 20-25\%$ less C and $s$-process elements ejected than from a population composed of only single stars, and we find little change in the N and O yields. We also compare our models with observed abundances from Ba stars and find our models can reproduce most Ba star abundances, but our population estimates a higher frequency of Ba stars with a surface [Ce/Y] > $+0.2\,$dex. Our models also predict the rare existence of Ba stars with masses $> 10 \text{M}\,_\odot$.