Overall Spectral Properties of Prompt Emissions with Diverse Segments in Swift/BAT Short Gamma-ray Bursts

TL;DR

This study analyzes the spectral and temporal properties of different emission segments in short gamma-ray bursts, revealing correlations and differences that suggest shared radiation mechanisms but diverse physical processes.

Contribution

It provides a comprehensive analysis of prompt emission components in sGRBs, highlighting their spectral properties and correlations, which was previously unclear.

Findings

Peak energies are uncorrelated with pulse durations.

No obvious spectral evolution across emission segments.

Main peaks are brighter than precursors and extended emissions.

Abstract

Owing to lack of multiple components of prompt $\gamma$-ray emissions in short gamma-ray bursts (sGRBs), how these distinct components are correlated still keeps unclear. In this paper, we investigate the spectral and temporal properties of precursors, main peaks and extended emissions in 26 sGRBs including GRB 170817A. It is found that peak energies ($E_p$) in each pulse are uncorrelated with the pulse duration ($t_{dur}$). Meanwhile, we find that there is no obvious correlation between peak energy and energy fluence. Interestingly, there is no obvious spectral evolution from earlier precursors to later extended emissions in view of the correlations of $t_{dur}$ with either the $E_p$ or the low energy spectrum index, $\alpha$. A power-law correlation between the average flux ($F_{p}$) and the energy fluence ($S_\gamma$), $log F_p=(0.62\pm0.07) log S_\gamma + (0.27\pm0.07)$, is found to exist in the individual segments instead of mean peaks previously. Furthermore, we also find that the main peaks are on average brighter than the precursors or the extend emissions about one order of magnitude. On the basis of all the above analyses, one can conclude that three emissive components would share the same radiation mechanisms but they might be dominated by diverse physical processes.