Maximum mass of compact stars from gravitational wave events with finite-temperature equations of state
Sanika Khadkikar, Ad. R. Raduta, Micaela Oertel, Armen Sedrakian
Abstract
We conjecture and verify a set of relations between global parameters of hot and fast-rotating compact stars which do not depend on the equation of state, 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 $2.{15}_{\ensuremath{-}0.17}^{+0.18}\ensuremath{\le}{M}_{\mathrm{TOV}}^{★}/{M}_{\ensuremath{\bigodot}}\ensuremath{\le}2.{24}_{\ensuremath{-}0.44}^{+0.45}$ for the typical range of entropy per baryon, $2\ensuremath{\le}S/A\ensuremath{\le}3$, 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.