Maximum mass of compact stars from gravitational wave events with finite-temperature equations of state

Abstract

We conjecture and verify a set of universal relations between global parameters of hot and fast-rotating compact stars, including a relation connecting the masses of the mass-shedding (Kepler) and static configurations. We apply these relations to the GW170817 event by adopting the scenario in which a hypermassive compact star remnant formed in a merger evolves into a supramassive compact star that collapses into a black hole once the stability line for such stars is crossed. We deduce an upper limit on the maximum mass of static, cold neutron stars $2.15_{-0.07}^{+0.10}\le M_{\mathrm{TOV}}^{\star }\le 2.24_{-0.10}^{+0.12}$ for the typical range of entropy per baryon $2\le S/A\le 3$ and electron fraction $Y_e=0.1$ characterizing the hot hypermassive star. Our result implies that accounting for the finite temperature of the merger remnant relaxes previously derived constraints on the value of the maximum mass of a cold, static compact star.

Comments: 17 pages, 11 figures