Prospects for Detecting Fast Radio Bursts in Globular Clusters of Nearby Galaxies

TL;DR

This paper predicts the detectability of fast radio bursts originating from globular clusters in nearby galaxies, especially M87, and explores white dwarf mergers as a potential formation mechanism for these FRBs.

Contribution

It provides the first detailed predictions for FRB detection rates in nearby galaxies' globular clusters and investigates white dwarf mergers as a plausible FRB source.

Findings

M87's globular cluster system likely contains about 10 FRB sources.

A 10-hour radio survey with FAST or MeerKat has a 90% chance to detect an FRB in M87.

White dwarf mergers in globular clusters could explain the observed FRB properties.

Abstract

The recent detection of a repeating fast radio burst (FRB) in an old globular cluster in M81 challenges traditional FRB formation mechanisms based on magnetic activity in young neutron stars formed recently in core-collapse supernovae. Furthermore, the detection of this repeater in such a nearby galaxy implies a high local universe rate of similar events in globular clusters. Building off the properties inferred from the M81 FRB, we predict the number of FRB sources in nearby ($d \lesssim 20\,$Mpc) galaxies with large globular cluster systems known. Incorporating the uncertain burst energy distribution, we estimate the rate of bursts detectable in these galaxies by radio instruments such as FAST and MeerKat. Of all local galaxies, we find M87 is the best candidate for FRB detections. We predict M87's globular cluster system contains $\mathcal{O}(10)$ FRB sources at present and that a dedicated radio survey (by FAST or MeerKat) of $\mathcal{O}(10)\,$hr has a $90\%$ probability of detecting a globular cluster FRB in M87. The detection of even a handful of additional globular cluster FRBs would provide invaluable constraints on FRB mechanisms and population properties. Previous studies have demonstrated young neutron stars formed following collapse of dynamically-formed massive white dwarf binary mergers may provide the most natural mechanism for these bursts. We explore the white dwarf merger scenario using a suite of $N$-body cluster models, focusing in particular on such mergers in M87 clusters. We describe a number of outstanding features of this scenario that in principle may be testable with an ensemble of observed FRBs in nearby globular clusters.