The statistical characteristics of the prompt emission lightcurves of gamma-ray bursts

Abstract

We fitted 75 pulses from 44 gamma-ray burst (GRB) prompt emission lightcurves, including four short ones and 40 long ones. Each pulse is fitted by a fast-rising exponential-decay (FRED) model. The statistical properties of these pulses are analyzed and compared with previous works. We found that the FRED model is almost suitable to describe all the pulses. We reconfirmed that there is a linear correlation between the full width at half maximum $\text{FWHM}$ and the pulse rising time $T_{\text{rise}}$, which supports the idea that the individual pulse is emitted at once within one explosion. Moreover, we found that several pulses do not obey the $\text{FWHM}-T_{\text{rise}}$ correlation, this implies that the radiation process of the prompt emission especially in the multi-pulse GRBs might involve more than one type and even possibly change with time. The innovation of this work lies in examining the statistical characteristics of lightcurves of both long and short-duration GRBs and re-evaluating the applicability of empirical relationships discovered by predecessors to both types of GRBs while paying special attention to the existence of outlier pulses. This work has positive implications for further exploring the diversity of GRB prompt radiation mechanisms.