Average curves of emissivity of the highest pulses in long and short gamma-ray bursts

Abstract

The average curves of emissivity (ACEs) of the highest pulses in long and short groups of gamma-ray bursts(GRBs) observed by BATSE on board CGRO have been studied by an alignment method and a wavelet package de-noising technique. A developed pulse-finding has been applied to identify the highest pulses from the profiles of GRBs. A sample including 116 long GRBs and 95 short GRBs was selected. The results show that the ACEs of the pulses in the short group are shorter and narrower than that in the long group. The ACEs of pulses in two groups have a significant difference, which was measured by the K-S test. Compared to the ACEs, the normalized ACEs of the pulses in the two groups seem to be similar. We present a brief discussion of our results. Based on our results and the discussion, we conclude that two groups of bursts may be generated from different sizes of emission regions. These sources likely have an intrinsic difference. However, the emission mechanisms are the same. These results support the most accepted taxonomy of GRBs, and present an interpretation of why two groups of bursts have a notable difference in the burst's duration, but other observed properties have no distinguishable difference.