Effects of axions on Nucleosynthesis in massive stars

TL;DR

This study examines how axion cooling influences nucleosynthesis in massive stars, revealing that axions can significantly alter element production and potentially tighten constraints on axion properties.

Contribution

It demonstrates the impact of axion cooling on stellar nucleosynthesis and suggests more stringent limits on axion-photon coupling from heavy element abundances.

Findings

Axion cooling suppresses nuclear reactions in key burning phases.

Larger amounts of neon and magnesium remain unprocessed before supernova.

Even with a small coupling constant, element abundances are significantly affected.

Abstract

We investigate the effect of the axion cooling on the nucleosynthesis in a massive star with $16M_{\odot}$ by standard stellar evolution calculation. We find that the axion cooling suppresses the nuclear reactions in carbon, oxygen and silicon burning phases because of the extraction of the energy. As a result, larger amounts of the already synthesized neon and magnesium remain without being consumed to produce further heavier elements. Even in the case with the axion-photon coupling constant $g_{a\gamma}= 10^{-11}$ GeV$^{-1}$, which is six times smaller than the current upper limit, the amount of neon and magnesium that remain just before the core-collapse supernova explosion is considerably larger than the standard value. This implies that we could give a more stringent constraint on $g_{a\gamma}$ from the nucleosynthesis of heavy elements in massive stars.