A Simple Law for the Average Time History of Gamma-Ray Bursts and Their Time Dilations

Abstract

Individual gamma ray bursts (GRBs) have very diverse time behavior - from a single pulse to a long complex sequence of chaotic pulses of different timescales. I studied light curves of GRBs using data from the CGRO's BATSE experiment and found that the average post-peak time history for a sample of 460 bursts obeys an unique and simple analytical law: $I\sim \exp (-(t/t_0{)}^{1/3})$ where $t$ is time measured from the peak of the event and $t_0$ is a constant ranging from 0.3 sec for strong bursts to $\sim 1$ sec for weak bursts. The average peak aligned profile follows this law with good accuracy in the whole range availible for analysis (from fractions of a second to $\sim$ 150 seconds after the peak). Such a law with a single time constant characterising the overall sample of GRBs should have important physical meaning. The dependence of $t_0$ versus brightness of GRBs is presented. The fact that $t_0$ depends on the brightness apparantly confirms the recently discovered effect of time dilation of weak bursts which has a possible cosmological interpretation. The time dilation is detected at a confidence level of $7\sigma$ and it is slightly larger than was previously reported.

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Cited by in corpus (7)

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• Evidence for Chain Reaction in the Time Profiles of Gamma Ray Bursts
• Study of Very Short Gamma-Ray Bursts
• A Complexity-Brightness Correlation in Gamma Ray Bursts
• Brightness Dependent Properties of Gamma Ray Bursts
• Average Emissivity Curve of BATSE Gamma-Ray Bursts with Different Intensities
• Long gamma-ray burst light curves as the result of a common stochastic pulse-avalanche process