The maximum mass of a neutron star is one of the most fundamental quantities in nuclear astrophysics. It marks the boundary between a neutron star and a black hole, and places direct constraints on the stiffness of dense matter at extreme densities. Gravitational wave observations of binary neutron star mergers, particularly signals that show a post-merger collapse, give us a rare observational window onto this threshold.

This paper extends maximum mass constraints to finite temperature equations of state, which matter for the hot dense remnant formed immediately after a merger. Using GW170817 and its multi-messenger counterparts, we derive bounds on the maximum mass of both cold and hot neutron stars. We show that thermal effects can shift the inferred maximum mass by up to roughly ten percent and need to be accounted for in any equation of state analysis.

Published in Physical Review C (2021)