Evidences for two Gamma-Ray Burst afterglow emission regimes

TL;DR

This study analyzes X-ray and optical afterglow fluxes of Gamma-Ray Bursts, revealing two distinct classes in X-ray emissions likely corresponding to different physical regimes, with optical data showing discrepancies possibly due to local absorption.

Contribution

The paper provides evidence for two distinct afterglow emission regimes in GRBs, interpreted as radiative and adiabatic behaviors within the fireball model, based on corrected flux correlations.

Findings

Good correlation in X-ray afterglows indicating two classes

No correlation observed in optical afterglows

Absorption near sources may affect optical observations

Abstract

We applied cosmological and absorption corrections to the X-ray and optical afterglow fluxes of a sample of Gamma-Ray Burst sources of known distance. We find a good correlation in X-rays and that the GRBs in our sample form two well defined classes. We tentatively interpret them as radiative and adiabatic afterglow behaviours in the framework of the fireball model for GRBs. We do not observe this correlation at optical wavelengths. This discrepancy with the model may be due to the absorption in the source vicinity.