GRB 180618A light curves

Our observations from gamma rays to optical wavelengths are consistent with a hot nebula expanding at relativistic speeds, powered by the plasma winds from a newborn, rapidly spinning and highly magnetized neutron star (i.e., a millisecond magnetar), whose rotational energy is released at a rate L_th_{prop.to}t^-(2.22+/-0.14)^ to reheat the unbound merger-remnant material. These results suggest that such neutron stars can survive the collapse to a black hole on timescales much larger than a few hundred milliseconds after the merger and power the GRB itself through accretion.

Bright thermal optical counterparts to binary merger gravitational wave sources may be common in future wide-field fast-cadence sky surveys.