Revisiting constraints on the maximum neutron star mass in light of GW190814

We investigate the maximum neutron star mass based on constraints from low-energy nuclear physics, neutron star tidal deformabilities from GW170817, and simultaneous mass-radius measurements of PSR J0030+045 from NICER. Our prior distribution is based on a combination of nuclear modeling valid in the vicinity of normal nuclear densities together with the assumption of a maximally stiff equation of state at high densities. The transition density is treated as a model parameter with uniform prior. Bayesian likelihood functions involving measured neutron star tidal deformabilities and radii are subsequently used to generate equation of state posteriors. We demonstrate that a modification of the highly uncertain supra-saturation density equation of state allows for the support of $2.5-2.6\,M_\odot$ neutron stars without strongly modifying the properties (radius, tidal deformability, and moment of inertia) of $\sim 1.4\,M_\odot$ neutron stars. However, the properties of neutron stars with masses $\sim 2.0\,M_\odot$ are significantly different under the two competing assumptions that the GW190814 secondary was a black hole or a neutron star.