Gamma-Ray Burst at the extreme: "the naked-eye burst" GRB 080319B

TL;DR

This paper reports on the observation of the extremely luminous gamma-ray burst GRB 080319B, highlighting its unique optical and gamma-ray features, and supports the synchrotron self-Compton model as the mechanism behind such bursts.

Contribution

It provides comprehensive multi-color optical follow-up data of the brightest optical transient ever recorded, offering new insights into the emission mechanisms of gamma-ray bursts.

Findings

Optical flux far exceeds gamma-ray flux, inconsistent with single emission models.

Correlated optical and gamma-ray variability suggests complex emission processes.

Spectral evolution indicates large angle emission and forward shock components.

Abstract

On 19 March 2008, the northern sky was the stage of a spectacular optical transient that for a few seconds remained visible to the naked eye. The transient was associated with GRB 080319B, a gamma-ray burst at a luminosity distance of about 6 Gpc (standard cosmology), making it the most luminous optical object ever recorded by human kind. We present comprehensive sky monitoring and multi-color optical follow-up observations of GRB 080319B collected by the RAPTOR telescope network covering the development of the explosion and the afterglow before, during, and after the burst. The extremely bright prompt optical emission revealed features that are normally not detectable. The optical and gamma-ray variability during the explosion are correlated, but the optical flux is much greater than can be reconciled with single emission mechanism and a flat gamma-ray spectrum. This extreme optical behavior is best understood as synchrotron self-Compton model (SSC). After a gradual onset of the gamma-ray emission, there is an abrupt rise of the prompt optical flux suggesting that variable self-absorption dominates the early optical light curve. Our simultaneous multi-color optical light curves following the flash show spectral evolution consistent with a rapidly decaying red component due to large angle emission and the emergence of a blue forward shock component from interaction with the surrounding environment. While providing little support for the reverse shock that dominates the early afterglow, these observations strengthen the case for the universal role of the SSC mechanism in generating gamma-ray bursts.