2020ApJ...892...55J

Very recently the NICER collaboration published the first-ever accurate measurement of mass and radius together for PSR J0030+0451, a nearby isolated quickly rotating neutron star (NS). In this work we set the joint constraints on the equation of state (EoS) and some bulk properties of NSs with the data of PSR J0030+0451, GW170817, and some nuclear experiments. The piecewise polytropic expansion method and the spectral decomposition method have been adopted to parameterize the EoS. The resulting constraints are consistent with each other. Assuming the maximal gravitational mass of nonrotating NS M_TOV lies between 2.04M_☉ and 2.4M_☉, with the piecewise method the pressure at twice nuclear saturation density is measured to be 3.19_–1.35^+2.63×10³⁴dyncm^–2 at the 90% level. For an NS with canonical mass of 1.4M_☉, we have the moment of inertia I_1.4=1.43_–0.13^+0.30×10³⁸kg⋅m², tidal deformability Λ_1.4=370_–130⁺³⁶⁰, radius R_1.4=12.1_–0.8^+1.2km, and binding energy BE_1.4=0.16_–0.02^+0.01M_☉ at the 90% level, which are improved in comparison to the constraints with the sole data of GW170817. These conclusions are drawn for the mass/radius measurements of PSR J0030+0451 by Riley et al. For the measurements of Miller et al., the results are rather similar.