Constraints On Short, Hard Gamma-Ray Burst Beaming Angles From Gravitational Wave Observations

TL;DR

This paper develops a method to constrain the beaming angles of short gamma-ray bursts using gravitational wave and electromagnetic observations of neutron star mergers, providing bounds on the jet opening angles.

Contribution

It introduces a novel approach to estimate gamma-ray burst beaming angles by comparing gravitational wave detections with electromagnetic observations.

Findings

Constraints on beaming angles could be as tight as 2.88° to 14.15° with current GW data.

Future observations at design sensitivity could improve these constraints to 8.10° to 14.95°.

Method demonstrates potential for understanding gamma-ray burst jet geometry.

Abstract

The first detection of a binary neutron star merger, GW170817, and an associated short gamma-ray burst confirmed that neutron star mergers are responsible for at least some of these bursts. The prompt gamma ray emission from these events is thought to be highly relativistically beamed. We present a method for inferring limits on the extent of this beaming by comparing the number of short gamma-ray bursts observed electromagnetically to the number of neutron star binary mergers detected in gravitational waves. We demonstrate that an observing run comparable to the expected Advanced LIGO 2016--2017 run would be capable of placing limits on the beaming angle of approximately $\theta \in (2.88^\circ,14.15^\circ)$, given one binary neutron star detection. We anticipate that after a year of observations with Advanced LIGO at design sensitivity in 2020 these constraints would improve to $\theta \in (8.10^\circ,14.95^\circ)$.