Effects of axions on nucleosynthesis in massive stars

Abstract

We investigate the effect of axion cooling on nucleosynthesis in a massive star with $16{M}_{\ensuremath{\bigodot}}$ by a standard stellar evolution calculation. We find that axion cooling suppresses 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 axion-photon coupling constant ${g}_{a\ensuremath{\gamma}}={10}^{\ensuremath{-}11}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$, 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 ${g}_{a\ensuremath{\gamma}}$ from the nucleosynthesis of heavy elements in massive stars.