Neutron Capture in Low‐Mass Asymptotic Giant Branch Stars: Cross Sections and Abundance Signatures

TLDR

Improved neutron‑capture cross sections for neutron‑magic nuclei at N = 82, especially 142Nd, provide a sensitive test for s‑process nucleosynthesis models. The study focuses on a consistent description of s‑process branchings among rare‑earth elements. New neutron‑capture cross‑section data for 142Nd contradict the classical exponential neutron‑exposure model yet improve agreement with solar s‑process abundances, demonstrate that abundance uncertainties are dominated by stellar modeling, and allow testing of stellar mass, metallicity, and the 13C neutron source.

Abstract

The recently improved information on the stellar (n,gamma) cross sections of neutron-magic nuclei at N = 82, and in particular of 142Nd, turned out to represent a sensitive test for models of s-process nucleosynthesis. While these data were found to be incompatible with the classical approach based on an exponential distribution of neutron exposures, they provide significantly better agreement between the solar abundance distribution of s nuclei and the predictions of models for low mass AGB stars. Particular attention is paid to a consistent description of s-process branchings in the region of the rare earth elements. It is shown that - in certain cases - the nuclear data are sufficiently accurate that the resulting abundance uncertainties can be completely attributed to stellar modelling. Thus, the s process becomes important for testing the role of different stellar masses and metallicities as well as for constraining the assumptions for describing the low neutron density provided by the 13C source.