A Search for Correlations between Gamma-Ray Burst Variability and Afterglow Onset

TL;DR

This study investigates whether there is a correlation between gamma-ray burst variability and the onset of optical afterglow emission, finding no statistical evidence of such a relationship across 76 GRBs.

Contribution

The paper provides the first systematic analysis comparing gamma-ray variability with optical afterglow onset times and shapes, revealing no significant correlation.

Findings

No correlation between gamma-ray variability and afterglow onset time.

No relationship between variability and the shape of the afterglow rise.

Results suggest independence of prompt emission irregularities and afterglow development.

Abstract

We compared the time (or time limit) of onset for optical afterglow emission to the gamma-ray variability V in 76 GRBs with redshifts. In the subset (25 cases) with the rise evident in the data, we fit the shape of the onset peak as well and compared the rising and decaying indices to V. We did not find any evidence for any patterns between these properties and there is no statistical support for any correlations. This indicates a lack of connection between irregularities of the prompt gamma-ray emission and the establishment of the afterglow phase. In the ordinary prompt internal shocks interpretation, this would indicate a lack of relationship between V and the bulk Lorentz factor of the event.