A candidate coherent radio flash following a neutron star merger

In this paper, we present rapid follow-up observations of the short GRB 201006A, consistent with being a compact binary merger, using the LOw Frequency ARray (LOFAR). We have detected a candidate 5.6σ⁠, short, coherent radio flash at 144 MHz at 76.6 min post-GRB with a 3
duration of 38 s. This radio flash is 27 arcsec offset from the GRB location, which has a probability of being co-located with the GRB of ∼0.05 per cent (3.8σ⁠) when accounting for measurement uncertainties. Despite the offset, we show that the probability of finding an unrelated transient within 40 arcsec of the GRB location is < 10^-6 and conclude that this is a candidate radio counterpart to GRB 201006A. We performed image plane dedispersion and the radio flash is tentatively (2.4σ⁠) shown to be highly dispersed, allowing a distance estimate, corresponding to a redshift of 0.58±0.06⁠. The corresponding luminosity of the event at this distance is
6.7^+6.6_-4.4 x10³² erg s^-1 Hz^-1⁠. If associated with GRB 201006A, this emission would indicate prolonged activity from the central engine that is consistent with being a newborn, supramassive, likely highly magnetized, millisecond spin neutron star (a magnetar).