A Common Stochastic Process Rules Gamma-ray Burst Prompt Emission and X-ray Flares
Journal
Date Issued
2015
Author(s)
Description
We are grateful to the anonymous referee for a constructive and insightful review. The PRIN MIUR project on “Gamma-ray bursts: From progenitors to physics of the prompt emission process,” P.I. F. Frontera (Prot. 2009 ERC3HT), is acknowledged.
Abstract
Prompt γ-ray and early X-ray afterglow emissions 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 γ-rays. However, the physical mechanism that leads to the complex temporal distribution of γ-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 four decades with an index of about two 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 (≥slant 8) γ-ray pulses are very unlikely to be accompanied by X-ray flares after the end of the prompt emission (3.1σ Gaussian confidence). These results are consistent with a simple interpretation: a 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 γ-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.
Volume
801
Issue
1
Start page
57
Issn Identifier
0004-637X
Ads BibCode
2015ApJ...801...57G
Rights
open.access
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