Origins of Short Gamma-Ray Bursts Deduced from Offsets to Their Host Galaxies Revisited

TL;DR

This study analyzes the spatial distribution of short gamma-ray bursts within their host galaxies to infer their origins, suggesting a significant fraction originate from merger events rather than solely from massive star formation.

Contribution

It provides a quantitative estimate of the fractions of short GRBs originating from mergers versus star formation, based on their offsets in different galaxy types.

Findings

Approximately 37% of short GRBs are linked to massive star components.

About 82% of short GRBs occur in late-type host galaxies.

Results support a mixed origin for short GRBs, including mergers and star formation.

Abstract

The spatial distribution of short Gamma-ray bursts (GRBs) in their host galaxies provide us an opportunity to investigate their origins. Based on the currently observed distribution of short GRBs relative to their host galaxies, we obtain the fraction of the component that traces the mergers of binary compact objects and the one that traces star formation rate (such as massive stars) in early- and late-type host galaxies. We find that the fraction of massive star component is 0.37\pm 0.13 from the analysis of projected offset distribution. This suggests that a good fraction of short GRBs still originate from merger events. From our analysis, we also conclude that the fraction of late-type hosts among the elliptical, starburst and spiral galaxy is 0.82\pm 0.05, which is consistent with the observed early- to late-type number ratio of host galaxies.