Analysis of 26 Barium Stars II. Contributions of s-, r- and p-processes in the production of heavy elements

TL;DR

This study quantifies the contributions of s-, r-, and p-processes to heavy element abundances in 26 barium stars, revealing insights into nucleosynthesis and binary star evolution.

Contribution

It provides a detailed analysis of the relative contributions of different nucleosynthesis processes in barium stars, using abundance ratios and neutron exposure models, which was not previously done for this sample.

Findings

Material from companion stars had solar-like isotopic composition.

Heavy element abundance ratios are similar to post-AGB stars.

Barium stars are enriched in r-elements, supporting binarity hypothesis.

Abstract

Barium stars show enhanced abundances of the slow neutron capture (s-process) heavy elements, and for this reason they are suitable objects for the study of s-process elements. The aim of this work is to quantify the contributions of the s-, r- and p-processes for the total abundance of heavy elements from abundances derived for a sample of 26 barium stars. The abundance ratios between these processes and neutron exposures were studied. The abundances of the sample stars were compared to those of normal stars thus identifying the fraction relative to the s-process main component. The fittings of the sigmaN curves (neutron capture cross section times abundance, plotted against atomic mass number) for the sample stars suggest that the material from the companion asymptotic giant branch star had approximately the solar isotopic composition as concerns fractions of abundances relative to the s-process main component. The abundance ratios of heavy elements, hs, ls and s and the computed neutron exposure are similar to those of post-AGB stars. For some sample stars, an exponential neutron exposure fits well the observed data, whereas for others, a single neutron exposure provides a better fit. The comparison between barium and AGB stars supports the hypothesis of binarity for the barium star formation. Abundances of r-elements that are part of the s-process path in barium stars are usually higher than those in normal stars,and for this reason, barium stars seemed to be also enriched in r-elements, although in a lower degree than s-elements. No dependence on luminosity classes was found in the abundance ratios behaviour among the dwarfs and giants of the sample barium stars.