Nucleosynthesis in the first massive stars

TL;DR

This paper explores nucleosynthesis in the first massive stars, emphasizing the role of mixing and rotation at low metallicity, and how these processes influence the chemical composition of ancient, iron-poor stars.

Contribution

It demonstrates that rotating stellar models at very low metallicity can explain mixing and surface enrichment in first massive stars, impacting early universe chemical evolution.

Findings

Mixing between H-burning and He-burning zones is necessary in first massive stars.

Surface layers of these stars enrich the material forming ancient stars.

The [Mg/Al] ratio is sensitive to the Na(23)(p,)Mg(24) reaction rate.

Abstract

The nucleosynthesis in the first massive stars may be constrained by observing the surface composition of long-lived very iron-poor stars born around 10 billion years ago from material enriched by their ejecta. Many interesting clues on physical processes having occurred in the first stars can be obtained just based on nuclear aspects. Two facts are particularly clear, 1) in these first massive stars, mixing must have occurred between the H-burning and the He-burning zone during their nuclear lifetimes; 2) only the outer layers of these massive stars have enriched the material from which the very iron-poor stars, observed today in the halo, have formed. These two basic requirements can be obtained by rotating stellar models at very low metallicity. In the present paper, we discuss the arguments supporting this view and illustrates the sensitivity of the results concerning the [Mg/Al] ratio on the rate of the reaction Na(23)(p,\gamma)Mg(24).