Neutrino-Driven Outflows and the Elemental Abundance Patterns of Very Metal-Poor Stars

TL;DR

This study investigates how neutrino-driven supernova outflows influence the elemental abundance patterns of very metal-poor stars, aiming to understand the nucleosynthesis processes responsible for elements between strontium and silver.

Contribution

It combines astrophysical models with observational data to constrain supernova ejecta conditions and identify the nucleosynthesis pathways for different element groups.

Findings

Neutron-rich outflows better reproduce Sr-Zr abundances.

Proton-rich outflows better match Mo-Pd abundances.

Certain supernova conditions consistently explain observed elemental patterns.

Abstract

The elemental abundances between strontium and silver ($Z = 38-47$) observed in the atmospheres of very metal-poor stars (VMP) in the Galaxy may contain the fingerprint of the weak $r$-process and $\nu p$-process occurring in early core-collapse supernovae explosions. In this work, we combine various astrophysical conditions based on a steady-state model to cover the richness of the supernova ejecta in terms of entropy, expansion timescale, and electron fraction. The calculated abundances based on different combinations of conditions are compared with stellar observations with the aim of constraining supernova ejecta conditions. We find that some conditions of the neutrino-driven outflows consistently reproduce the observed abundances of our sample. In addition, from the successful combinations, the neutron-rich trajectories better reproduce the observed abundances of Sr-Zr ($Z= 38-40$), while the proton-rich ones, Mo-Pd ($Z= 42-47$).