Naked-eye optical flash from GRB 080319B: Tracing the decaying neutrons in the outflow

TL;DR

This paper explains the naked-eye optical flash from GRB 080319B as resulting from neutron decay and subsequent interaction with late ejected proton shells in the GRB outflow.

Contribution

It introduces a model linking neutron decay in GRB outflows to observable optical flashes, providing a new explanation for bright optical emissions.

Findings

Optical flash from GRB 080319B can be explained by neutron decay products.

Neutron decay occurs at larger radii, influencing late-time optical emission.

Model matches observed brightness and timing of the optical flash.

Abstract

For an unsteady baryonic gamma-ray burst (GRB) outflow, the fast and slow proton shells collide with each other and produce energetic soft gamma-ray emission. If the outflow has a significant neutron component, the ultra-relativistic neutrons initially expand freely until decaying at a larger radius. The late time proton shells ejected from the GRB central engine, after powering the regular internal shocks, will sweep these $\beta-$decay products and give rise to very bright UV/optical emission. The naked-eye optical flash from GRB 080319B, an energetic explosion in the distant universe, can be well explained in this way.