Constraining the Dense Matter Equation of State with Joint Analysis of NICER and LIGO/Virgo Measurements

The Neutron Star Interior Composition Explorer collaboration recentlypublished a joint estimate of the mass and the radius of PSR J0030+0451,derived via X-ray pulse-profile modeling. Raaijmakers et al. exploredthe implications of this measurement for the dense matter equation ofstate (EOS) using two parameterizations of the high-density EOS: apiecewise-polytropic model, and a model based on the speed of sound inneutron stars (NSs). In this work we obtain further constraints on theEOS following this approach, but we also include information about thetidal deformability of NSs from the gravitational wave signal of thecompact binary merger GW170817. We compare the constraints on the EOS tothose set by the recent measurement of a 2.14 M_⊙ pulsar,included as a likelihood function approximated by a Gaussian, and find asmall increase in information gain. To show the flexibility of ourmethod, we also explore the possibility that GW170817 was a NS-blackhole merger, which yields weaker constraints on the EOS.