Pregalactic LiBeB Production by Supernova Cosmic Rays

TL;DR

This paper models the production of light elements Be and B by cosmic rays from early supernovae, suggesting their abundances in metal-poor stars could reveal pregalactic nucleosynthesis processes.

Contribution

It introduces a detailed calculation of Be and B production in the pregalactic universe using cosmic ray inputs from a cosmic chemical evolution model.

Findings

Be and B produced with $^6$Li match the lowest observed levels in metal-poor stars.

Early cosmic ray nucleosynthesis could explain observed $^6$Li abundances.

Observation of Be and B in stars with [Fe/H] ≤ -3 is crucial for understanding pregalactic nucleosynthesis.

Abstract

I calculate the evolution of Be and B abundances produced by cosmic rays generated by massive stars in the pregalactic phase of the universe. The inputs for calculation, i.e. the star formation rate and the nuclear abundances of cosmic rays, which I assume to be the same as those of the ISM, are taken from the results of a detailed cosmic chemical evolution model with its parameters best fitted from several items of observational information including an early reionization of the IGM by $z\sim 15$. I found that when the $^6$Li plateau abundance observed in metal-poor halo stars originated in the pregalactic cosmological cosmic ray nucleosynthesis, Be and B simultaneously produced with $^6$Li amount to the lowest levels ever detected in metal-poor halo stars. It is desirable to observe Be and B abundances in metal-poor halo stars with [Fe/H]$\leq -3$ in order to elucidate the possibility of early $^6$LiBeB production by pregalactic supernova cosmic ray nucleosynthesis.