Inferring jet physics from neutron star - black hole mergers with gravitational waves

TL;DR

This paper demonstrates how gravitational wave observations from neutron star-black hole mergers can be used to infer key jet-launching parameters, enhancing understanding of gamma-ray burst origins.

Contribution

It introduces a Bayesian hierarchical inference method to estimate the minimum remnant mass and viewing angle for gamma-ray burst jets from simulated gravitational wave data.

Findings

Minimum remnant mass can be measured within 0.01 solar masses.

Maximum gamma-ray burst viewing angle can be constrained within 13 degrees.

200 observations are sufficient for these inferences.

Abstract

Neutron star - black hole (NSBH) mergers that undergo tidal disruption may launch jets that could power a gamma-ray burst. We use a population of simulated NSBH systems to measure jet parameters from the gravitational waves emitted by these systems. The conditions during the tidal disruption and merger phase required to power a gamma-ray burst are uncertain. It is likely that the system must achieve some minimum remnant baryonic mass after the merger before a jet can be launched to power a gamma-ray burst. Assuming a fiducial neutron star equation of state, we show how Bayesian hierarchical inference can be used to infer the minimum remnant mass required to launch a gamma-ray burst jet as well as the maximum gamma-ray burst viewing angle to detect a gamma-ray burst. We find that with 200 NSBH observations, we can measure the minimum disk mass to within 0.01 solar masses at 90% credibility. We simultaneously infer the maximum gamma-ray burst viewing angle to within 13 degrees at 90% credibility. We conclude that upcoming upgrades to the LIGO observatories may provide important new insights into the physics of NSBH jets.