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Abstract

Motivated by the unknown nature of the 2.50-2.67 M-circle dot compact
object in the binary merger event GW190814, we study 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, a choice that enables us to
probe the connection between observed heavy neutron stars and the
transition density at which conventional nuclear physics models must
break down. We demonstrate that a modification of the highly uncertain
suprasaturation density equation of state beyond 2.64 times normal
nuclear density is required in order for chiral effective field theory
models to be consistent with current neutron star observations and the
existence of 2.6M(circle dot) neutron stars. We also show that the
existence of very massive neutron stars strongly impacts the radii of
approximate to 2.0M(circle dot) neutron stars (but not necessarily the
radii of 1.4M(circle dot) neutron stars), which further motivates future
NICER radius measurements of PSR J1614-2230 and PSR J0740+6620.