A common stochastic process rules gamma-ray burst prompt emission and X-ray flares

TL;DR

This paper demonstrates that the temporal distribution of gamma-ray pulses and X-ray flares in GRBs can be explained by a common stochastic process, revealing insights into the underlying physical mechanism of these astrophysical phenomena.

Contribution

It introduces a unified stochastic model for gamma-ray and X-ray emissions in GRBs, supported by analysis across multiple catalogs, linking prompt and flare emissions through a shared process.

Findings

Power-law tail in waiting time distribution with index ~2

GRBs with many gamma-ray pulses rarely have X-ray flares

A common Poisson process explains both prompt emission and flares

Abstract

Prompt gamma-ray and early X-ray afterglow emission in gamma-ray bursts (GRBs) are characterized by a bursty behavior and are often interspersed with long quiescent times. There is compelling evidence that X-ray flares are linked to prompt gamma-rays. However, the physical mechanism that leads to the complex temporal distribution of gamma-ray pulses and X-ray flares is not understood. Here we show that the waiting time distribution (WTD) of pulses and flares exhibits a power-law tail extending over 4 decades with index ~2 and can be the manifestation of a common time-dependent Poisson process. This result is robust and is obtained on different catalogs. Surprisingly, GRBs with many (>=8) gamma-ray pulses are very unlikely to be accompanied by X-ray flares after the end of the prompt emission (3.1 sigma Gaussian confidence). These results are consistent with a simple interpretation: an hyperaccreting disk breaks up into one or a few groups of fragments, each of which is independently accreted with the same probability per unit time. Prompt gamma-rays and late X-ray flares are nothing but different fragments being accreted at the beginning and at the end, respectively, following the very same stochastic process and likely the same mechanism.