Production of 9Be through alpha-fusion reaction of metal-poor cosmic ray and stellar flare

TL;DR

This paper investigates the production of 9Be through alpha-fusion reactions driven by cosmic rays and stellar flares in metal-poor environments, aiming to explain observed elemental abundances.

Contribution

It introduces a detailed model of 9Be synthesis via two-step alpha-fusion reactions involving CR and flare-accelerated helium isotopes in various astrophysical settings.

Findings

Predicted 9Be/6Li yield ratios vary with different nucleosynthesis scenarios.

Future observations could detect enhanced 9Be in metal-poor stars due to CR or flare activity.

The model links 9Be production to observable signatures in stellar spectra.

Abstract

Spectroscopic observations of metal-poor stars have indicated possible 6Li abundances that are much larger than the primordial abundance predicted in the standard big bang nucleosynthesis model. Possible mechanisms of 6Li production in metal-poor stars include pregalactic and cosmological cosmic ray (CR) nucleosynthesis and nucleosynthesis by flare-accelerated nuclides. We study 9Be production via two-step alpha-fusion reactions of CR or flare-accelerated 3,4He through 6He and 6,7Li, in pregalactic structure, intergalactic medium, and stellar surfaces. We solve transfer equations of CR or flare particles and calculate nuclear yields of 6He, 6,7Li, and 9Be taking account of probabilities of processing 6He and 6,7Li into 9Be via fusions with alpha particles. Yield ratios, i.e., 9Be/6Li, are then calculated for the CR and flare nucleosynthesis models. We suggest that the future observations of 9Be in metal-poor stars may find enhanced abundances originating from metal-poor CR or flare activities.