New constraints on the major neutron source in low-mass AGB stars

TL;DR

This study uses updated AGB star models and isotopic data from dust grains to refine the understanding of the main neutron source driving the s-process in low-mass AGB stars, highlighting the role of magnetic buoyancy in 13C-pocket formation.

Contribution

It introduces new constraints on the 13C neutron source in AGB stars by combining advanced models with isotopic grain data, emphasizing magnetic buoyancy effects.

Findings

Support for magnetic-buoyancy-induced 13C-pocket formation.

Consistency of Ni, Sr, and Ba grain data with the model.

Evidence for deep H mixing into the He-intershell.

Abstract

We compare updated Torino postprocessing asymptotic giant branch (AGB) nucleosynthesis model calculations with isotopic compositions of mainstream SiC dust grains from low-mass AGB stars. Based on the data-model comparison, we provide new constraints on the major neutron source, 13C({\alpha},n)16O in the He-intershell, for the s-process. We show that the literature Ni, Sr, and Ba grain data can only be consistently explained by the Torino model calculations that adopt the recently proposed magnetic-buoyancy-induced 13C-pocket. This observation provides strong support to the suggestion of deep mixing of H into the He-intershell at low 13C concentrations as a result of efficient transport of H through magnetic tubes.