What if the neutron star maximum mass is beyond $\sim2.3 M_{\odot}$?

Wu, Xuhao

By assuming the formation of a black hole soon after the merger event of GW170817, the maximum mass of stable neutron star, $M_{\rm{max}}\simeq 2.3~M_{\odot}$, is proposed by numerical relativity, but there is no solid evidence to rule out $M_\textrm{max}>2.3~M_{\odot}$ from the point of both microphysical and astrophysical views. It is naturally expected that the equation of state (EOS) would become stiffer beyond a specific density to explain massive pulsars.
We consider the possibility of EOSs with $M_\textrm{max}>2.3~M_{\odot}$, investigating the stiffness and the transition density in a polytropic model, for two kinds of neutron stars (i.e., gravity-bound and strong-bound stars on surface).