Quantifying the coincidence between gravitational waves and fast radio bursts from neutron star - black hole mergers

TL;DR

This paper investigates the potential for multi-messenger observations of neutron star-black hole mergers and fast radio bursts, demonstrating methods to confidently associate gravitational-wave signals with FRBs despite uncertainties.

Contribution

It introduces a statistical framework using posterior odds to identify coincident NSBH mergers and FRBs, emphasizing the importance of multiple observatories and specific SNR thresholds.

Findings

Significant posterior odds require at least two observatories.

A network SNR > 10 is needed for confident detection.

Coincident detections can differentiate FRB models.

Abstract

Fast radio bursts (FRBs) are mysterious astrophysical transients whose origin and mechanism remain unclear. Compact object mergers may be a promising channel to produce some FRBs. Neutron star-black hole (NSBH) mergers could produce FRBs through mechanisms involving neutron star tidal disruption or magnetospheric disturbances. This could present an opportunity for multi-messenger gravitational-wave observations, providing new insight into the nature of FRBs and nuclear matter. However, some of the gravitational-wave signals may be marginal detections with signal-to-noise ratios < 8 or have large sky location and distance uncertainties, making it less straightforward to confidently associate an FRB with the gravitational-wave signal. One must therefore take care to avoid a false positive association. We demonstrate how to do this with simulated data. We calculate the posterior odds -- a measurement of our relative belief for a common versus unrelated origin of a coincident NSBH and FRB. We find that a coincident FRB+NSBH from a common source can yield a statistically significant posterior odds in a network with at least two observatories, but only if we require a coincidence in time and and sky location, rather than time alone. However, we find that for our model, we require a network signal-to-noise ratio greater than 10 to be confident in the common-source detection, when using a threshold of ln odds > 8. We suggest that a coincident NSBH+FRB detection could help distinguish between FRB engines by discriminating between disrupting and non-disrupting models.