Origin of the bright prompt optical emission in the naked eye burst

TL;DR

This paper explores how internal shocks with variable Lorentz factors in relativistic jets can produce the intense optical emission observed in the Naked Eye Burst GRB 080319B, within the synchrotron emission framework.

Contribution

It proposes a novel scenario where variability in Lorentz factors leads to multiple internal shocks, explaining the bright optical prompt emission in GRB 080319B.

Findings

High Lorentz factor variability causes multiple internal shocks.

Less violent shocks produce optical emission.

Main gamma-ray emission arises from the most violent shocks.

Abstract

The huge optical brightness of GRB 080319B (the "Naked Eye Burst) makes this event really challenging for models of the prompt GRB emission. In the framework of the internal shock model, we investigate a scenario where the dominant radiative process is synchrotron emission and the high optical flux is due to the dynamical properties of the relativistic outflow: if the initial Lorentz factor distribution in the jet is highly variable, many internal shocks will form within the outflow at various radii. The most violent shocks will produce the main gamma-ray component while the less violent ones will contribute at lower energy, including the optical range.