paper

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

arXiv:1501.02706 · doi:10.1088/0004-637X/801/1/57

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.

arXiv comment11 pages, 7 figures, accepted by ApJ

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