GW170817 and GRB 170817A provided direct evidence that binary neutron star (NSNS) mergers can produce short gamma-ray bursts (sGRBs). However, questions remain about the nature of the central engine. Depending on the mass, the remnant from a NSNS merger may promptly collapse to a black hole, form a hypermassive neutron star (HMNS) which undergoes a delayed collapse to a BH, a supramassive neutron star (SMNS) with a much longer lifetime, or an indefinitely stable sub-supramassive NS. There is strong evidence that a BH with an accretion disk can launch a sGRB-compatible jet via the Blandford–Znajek mechanism, but whether a supramassive star can do the same is less clear.
I will present our latest set of general relativistic magnetohydrodynamics (GRMHD) simulations of the merger of both irrotational and spinning, equal-mass neutron star binaries. We examine cases with different initial binary masses, both a case which produces a HMNS which collapses to a BH, and lower mass binaries that produce SMNS remnants. We find similar "jet like" structures (helical magnetic field structures and mildly relativistic outflow from the poles) for both the SMNS and HMNS remnants. I will discuss whether these jet-like structures from SMNS remnants can also be the progenitors of sGRBs, as well as exploring the impact of NS spin and mass on the outcome.
