Constraints on AGB models from the heavy-element composition of presolar SiC grains

TL;DR

This paper uses precise measurements of presolar SiC grains to refine models of AGB stars, focusing on heavy element synthesis via the s process and implications for neutron capture reactions.

Contribution

It provides new constraints on AGB star models by analyzing heavy-element compositions in presolar SiC grains, highlighting the need to revise neutron capture cross sections and neutron source reactions.

Findings

Mo data suggest revising the 95Mo neutron capture cross section.

Zr data indicate 22Ne(alpha,n)25Mg is not the main neutron source.

Model predictions for Fe-peak elements offer future testing grounds.

Abstract

Presolar SiC grains formed around Asymptotic Giant Branch (AGB) stars during their carbon-rich phase and contain heavy elements in trace amounts showing the signature of the slow neutron capture process (s process). Thanks to recent advances in analysis techniques, SiC data now provide extremely precise information on neutron capture cross sections and AGB models. For example, high-precision data for Mo in single SiC grains indicate that a revision of the 95Mo neutron capture cross section is needed, while data for Zr indicates that the 22Ne(alpha,n)25Mg reaction cannot be a dominant neutron source for the s process in AGB stars. We present model predictions for the composition of Fe-peak elements in AGB stars. These elements could be analysed in the near future thus providing further stringent constraints to our understanding of AGB stars.