The Temporal Symmetrical and Translational Structure in Gamma-Ray Burst Light Curves

Abstract

Tremendous information is hidden in the light curve of a gamma-ray burst (GRB). Based on Compton Gamma Ray Observatory/Burst And Transient Source Experiment (BATSE) data, Hakkila found a majority of GRBs can be characterized by a smooth, single-peaked component superposed with a temporally symmetrical residual structure, i.e., a mirror feature for the fast-varying component. In this study, we conduct a similar analysis on the same data, as well as on Fermi/Gamma-Ray Burst Monitor data. We obtained a similar conclusion, which is that most GRBs have this symmetrical fast-varying component. Furthermore, we chose an alternative model to characterize the smooth component and used a three-parameter model to identify the residual, i.e., the fast component. By choosing 226 BATSE GRBs based on a few criteria, we checked the time-symmetrical feature and time-translational feature for the fast components and found the ratio is roughly 1:1. We propose that both features could come from the structure of the ejected shells. In the future, the Square Kilometre Array might be able to observe the early radio emission from the collision of the shells.