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

Tremendous information is hidden in the light curve of a gamma-ray burst (GRB). Based on CGRO/BATSE data, Hakkila (2021) 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/GBM data. We got a similar conclusion that most GRBs have this symmetrical fast varying component. Further more, 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. Future SKA might be able to observe the early radio emission from the collision of the shells.