Numerical relativity simulations of prompt collapse mergers: threshold mass and phenomenological constraints on neutron star properties after GW170817

Binary neutron star (BNS) mergers are one of the most violent events in our universe and one of the most important sources in current and future gravitational wave (GW) observatories. There is widespread understanding that mergers result in either a black hole following a prompt collapse or, a differentially rotating massive neutron star.

We determine the threshold mass for prompt collapse by performing a new set of 227 numerical relativity simulations with twenty-three phenomenological and microphysical finite temperature EOS. We combine the EOS-insensitive relations, phenomenological constraints on NS properties, and observational data from GW170817 to derive an improved lower limit on radii of maximum mass and 1.4 M⊙ NS of 9.81 km and 10.74 km, respectively. We introduce new methods to constrain the upper as well as the lower limit of NS maximum mass using future BNS detections and their identification as prompt or delayed collapse. With future observations, it will be possible to derive even tighter constraints on the properties of matter at and above nuclear density using the method proposed in this work.