Properties of Short Gamma-Ray Burst Pulses from A BATSE TTE GRB Pulse Catalog

TL;DR

This study analyzes pulse properties of short gamma-ray bursts from a new BATSE catalog, revealing their complex temporal behaviors, correlations, and supporting external shocks as the origin of prompt emission across GRB classes.

Contribution

It provides a comprehensive analysis of short GRB pulse properties, classifies their light curves by complexity, and links their behaviors to external shock models, introducing a new transient type.

Findings

Most short GRBs are single-pulsed.

Pulse durations predict interpulse separation and subsequent pulse durations.

External shocks likely produce the prompt emission in short GRBs.

Abstract

We analyze pulse properties of Short gamma-ray bursts (GRBs) from a new catalog containing 434 pulses from 387 BATSE Time-Tagged Event (TTE) GRBs. Short GRB pulses exhibit correlated properties of duration, fluence, hardness, and amplitude, and they evolve hard-to-soft while undergoing similar triple-peaked light curves similar to those found in Long/Intermediate bursts. We classify pulse light curves using their temporal complexities, demonstrating that Short GRB pulses exhibit a range of complexities from smooth to highly variable. Most of the bright, hard, chaotic emission seen in complex pulses seems to represent a separate highly-variable emission component. Unlike Long/Intermediate bursts, as many as 90\% of Short GRBs are single-pulsed. However, emission in Short multi-pulsed bursts is coupled such that the first pulse's duration is a predictor of both the interpulse separation and subsequent pulse durations. These results strongly support the idea that external shocks produce the prompt emission seen in Short GRBs. The similarities between the triple-peaked structures and spectral evolution of Long, Short, and Intermediate GRBs then suggests that external shocks are responsible for the prompt emission observed in all GRB classes. In addition to these findings, we identify a new type of gamma-ray transient in which peak amplitudes occur at the end of the burst rather than at earlier times. Some of these "Crescendo" bursts are preceded by rapid-fire "Staccato" pulses, whereas the remaining are preceded by a variable episode that could be unresolved staccato pulses.