2020ApJ...902...38Z

We use Stergioulas's RNS code for investigating fast pulsars with equations of state (EOSs) on the causality surface (where the speed of sound is equal to that of light) of the high-density EOS parameter space satisfying all known constraints from both nuclear physics and astrophysics. We show that one possible explanation for GW190814's secondary component, which has mass 2.50-2.67 M_☉, is that it is a superfast pulsar spinning faster than 971 Hz, about 42% below its Kepler frequency. If confirmed, it would be the fastest pulsar with the highest mass yet observed. There is a large and physically allowed EOS parameter space below the causality surface where pulsars heavier than 2.50 M_☉ are supported if they can rotate even faster with critical frequencies that depend strongly on the high-density behavior of nuclear symmetry energy.