Dependence of the Sr-to-Ba and Sr-to-Eu Ratio on the Nuclear Equation of State in Metal Poor Halo Stars

TL;DR

This paper models how the ratio of certain elements in metal-poor stars depends on the nuclear equation of state, using a truncated r-process scenario linked to core-collapse supernovae and black hole formation.

Contribution

It introduces a galactic chemical evolution model connecting element ratios to the nuclear equation of state through a truncated r-process in supernovae.

Findings

Upper limits in [Sr/Ba] relate to the nuclear equation of state.

Scatter in element ratios is consistent with turbulent supernova ejecta.

Model adaptations explain isotopic scatter via ejecta mixing.

Abstract

A model is proposed in which the light r-process element enrichment in metal-poor stars is explained via enrichment from a truncated r-process, or "tr-process." The truncation of the r-process from a generic core-collapse event followed by a collapse into an accretion-induced black hole is examined in the framework of a galactic chemical evolution model. The constraints on this model imposed by observations of extremely metal-poor stars are explained, and the upper limits in the [Sr/Ba] distributions are found to be related to the nuclear equation of state in a collapse scenario. The scatter in [Sr/Ba] and [Sr/Eu] as a function of metallicity has been found to be consistent with turbulent ejection in core collapse supernovae. Adaptations of this model are evaluated to account for the scatter in isotopic observables. This is done by assuming mixing in ejecta in a supernova event.