Nucleosynthesis in the Early Galaxy

TL;DR

This paper investigates the origins of element abundance patterns in the early galaxy, proposing a primary light element process (LEPP) that, combined with the r-process, explains observed non-uniformities in metal-poor stars and aligns with solar abundance data.

Contribution

It introduces the concept of a light element primary process (LEPP), characterizes its abundance pattern, and explores potential neutron capture sites with different neutron densities.

Findings

LEPP explains non-uniform element abundances in metal-poor stars.

The derived LEPP pattern aligns with missing solar abundance components.

Neutron densities of ≤10^{13} or ≥10^{24} cm^{-3} best fit the observations.

Abstract

Recent observations of r-process-enriched metal-poor star abundances reveal a non-uniform abundance pattern for elements $Z\leq47$. Based on non-correlation trends between elemental abundances as a function of Eu-richness in a large sample of metal-poor stars, it is shown that the mixing of a consistent and robust light element primary process (LEPP) and the r-process pattern found in r-II metal-poor stars explains such apparent non-uniformity. Furthermore, we derive the abundance pattern of the LEPP from observation and show that it is consistent with a missing component in the solar abundances when using a recent s-process model. As the astrophysical site of the LEPP is not known, we explore the possibility of a neutron capture process within a site-independent approach. It is suggested that scenarios with neutron densities $n_{n}\leq10^{13}$ $cm^{-3}$ or in the range $n_{n}\geq10^{24}$ $cm^{-3}$ best explain the observations.