Observational constraints on the nature of very short gamma-ray bursts

TL;DR

This paper investigates very short gamma-ray bursts, analyzing their spatial distribution, temporal profiles, and potential origins, suggesting they may originate from neutron star mergers or primordial black hole evaporation.

Contribution

It provides observational constraints on very short gamma-ray bursts, exploring their spatial distribution, temporal characteristics, and possible origins, which are previously not well understood.

Findings

No peculiarities in arrival times despite non-uniform distribution.

Burst shapes show no dependence on sky location.

Many VSBs have multiple peaks despite short durations.

Abstract

We discuss a very peculiar subgroup of gamma-ray bursts among the BATSE sources. These bursts are very short ($T_{90} \le $0.1 s), hard, and came predominantly from a restricted direction of the sky (close to the Galactic anti-center). We analyze their arrival times and possible correlations, as well as the profiles of individual bursts. We find no peculiarities in the arrival times of Very Short Bursts (VSBs) despite their highly non-uniform spatial distribution. There is no dependence in the burst shapes on location. Bursts coming both from the burst-enhancement Galactic Anticenter region and from all other directions show considerable dispersion in their rise and fall times. Significant fraction of VSBs have multiple peaks despite their extremely short duration. Burst time properties are most likely to be consistent with two origin mechanisms: either with binary NS-NS mergers with low total masses passing through a phase of hypermassive neutron star, or with evaporation of the primordial black holes in the scenario of no photosphere formation.