Light-element synthesis in high-entropy relativistic flows associated with gamma-ray bursts

We calculate and discuss the light-element freezeout and nonthermal reaction nucleosynthesis in high-entropy winds and fireballs for broad ranges of entropy per baryon, dynamic timescales characterizing relativistic expansion, and neutron-to-proton ratios. With conditions characteristic of gamma-ray bursts (GRBs), we find that deuterium production can be prodigious, with final abundance values H-2/Hgreater than or similar to2%, depending on the fireball isospin, late-time dynamics, and the effects of neutron-decoupling-induced high-energy nonthermal nuclear reactions. This implies that there could potentially be detectable local enhancements in the deuterium abundance associated with GRB events.