Supermassive neutron stars rule out twin stars

Abstract

We investigate the implications of a hypothetical $2.5\text{ }\text{ }{\mathrm{M}}_{\ensuremath{\bigodot}}$ neutron star in regard to the possibility of a first order phase transition to quark matter. We use equations of state (EoS) of varying stiffness provided by a parametrizable relativistic mean field model transitioning to a constant speed of sound EoS. We find a strong connection between the discontinuity in energy density and the maximal neutron star mass. We demonstrate, that high maximal masses cannot be realized for large discontinuities. As a result visible mass gaps, i.e., twin stars, and masses of ${M}_{\mathrm{max}}\ensuremath{\gtrsim}2.2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ are mutually exclusive.