# Neutron-Capture Elements in the Double-Enhanced Star HE 1305-0007: a New s- and r-Process Paradigm

## TL;DR

This paper studies the neutron-capture element abundances in the metal-poor star HE 1305-0007, proposing a new paradigm involving a single neutron exposure s-process and a possible r-process contribution from a binary evolution scenario.

## Contribution

It introduces a new model for double-enhanced stars, combining a single neutron exposure s-process with a potential r-process origin linked to binary evolution.

## Key findings

- Almost all s-elements formed in a single neutron exposure.
- The star likely experienced a post-common-envelope binary evolution.
- Possible r-process enrichment from an accretion-induced collapse event.

## Abstract

The star HE 1305-0007 is a metal-poor double-enhanced star with metallicity [Fe/H] $=-2.0$, which is just at the upper limit of the metallicity for the observed double-enhanced stars. Using a parametric model, we find that almost all s-elements were made in a single neutron exposure. This star should be a member of a post-common-envelope binary. After the s-process material has experienced only one neutron exposure in the nucleosynthesis region and is dredged-up to its envelope, the AGB evolution is terminated by the onset of common-envelope evolution. Based on the high radial-velocity of HE 1305-0007, we speculate that the star could be a runaway star from a binary system, in which the AIC event has occurred and produced the r-process elements.