An assessment of the Association Between a Fast Radio Burst and Binary Neutron Star Merger

Fast radio bursts (FRBs) are mysterious bright millisecond-duration radio bursts at cosmological distances. While young magnetars have been put forward as the leading source candidate, recent observations suggest there may be multiple FRB progenitor classes. It has long been theorised that FRBs could be emitted from compact object mergers - cataclysmic events such as binary neutron star (BNS) mergers that may be detectable in gravitational waves (GWs) by the ground-based Laser Interferometer Gravitational Wave Observatory (LIGO)and Virgo. Here we report a potential coincidence between the only BNS merger event GW190425 out of 21 GW sources detected during the first six months of LIGO-Virgo's 3rd Science Run and a bright, non-repeating FRB event, FRB 20190425A, from a search using public GW and CHIME FRB data. The FRB is located within the GW's sky localization area, occurred 2.5 hours after the GW event, and has a dispersion measure consistent with the distance inferred from GW parameter estimation. The chance probability of a coincidence between unrelated FRB and GW events in the databases is estimated to be 0.0052 ($2.8 \sigma$). We estimate the chance of CHIME detecting such an event to range from 0.4% for a beam-centre detection to 68% if a bright burst is detectable in a far sidelobe. This potential association is consistent with the theory that the BNS merger leaves behind a supramassive, highly magnetized compact object, which collapses to form a black hole after losing angular momentum due to spindown and makes an FRB through ejecting the magnetosphere. If such a physical association is established, the equation of state of the post-merger compact object is likely stiff, with a Tolman-Oppenheimer-Volkoff non-spinning maximum mass $M_{TOV} > 2.63_{-0.23}^{+0.39} M_\odot$ for a neutron star remnant, or $M_{TOV} > 2.31_{-0.08}^{+0.24} M_\odot$ for a quark star remnant.