Short gamma-ray bursts: evidence for an origin in globular clusters?

TL;DR

This paper investigates the origins of short gamma-ray bursts by comparing their observed positions relative to host galaxies with models, suggesting some may originate from neutron star mergers in globular clusters.

Contribution

It provides evidence that while most short gamma-ray bursts align with neutron star binary models, some may originate from dynamical mergers in globular clusters, indicating multiple formation channels.

Findings

Most bursts' offsets match the neutron star binary model.

Some bursts have larger-than-predicted offsets.

Potential link between large offsets and globular cluster origins.

Abstract

We compare the observed spatial offsets of short gamma-ray bursts from their host galaxies with their predicted distributions, assuming that they originate in double neutron star binaries that form from field stars. We find that, for the majority of bursts, this model is sufficient to explain the observed offsets, although there is a trend towards larger offsets than predicted. One burst, GRB 060502B, has an offset that is clearly anomalous. We discuss possible reasons for the large offsets, including host galaxy misidentification, and suggest that some of the largest-offset bursts may originate in the merger of double neutron star binaries that form dynamically in the cores of globular clusters.