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Abstract

The NICER collaboration recently published a joint estimate of the mass and
the radius of PSR J0030+0451, derived via X-ray pulse-profile modeling.
Raaijmakers et al. (2019) explored the implications of this measurement for the
dense matter equation of state (EOS) using two parameterizations of the
high-density EOS: a piecewise-polytropic model, and a model based on the speed
of sound in neutron stars. In this work we obtain further constraints on the
EOS following this approach, but we also include information about the tidal
deformability of neutron stars from the gravitational wave signal of the
compact binary merger GW170817. We compare the constraints on the EOS to those
set by the recent measurement of a 2.14 solar mass pulsar, included as a
likelihood function approximated by a Gaussian, and find a small increase in
information gain. To show the flexibility of our method, we also explore the
possibility that GW170817 was a neutron star-black hole merger, which yields
weaker constraints on the EOS.