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Abstract

Instead of parameterizing the pressure-density relation of a neutron star


(NS), one can parameterize its macroscopic properties such as mass ($M$),


radius ($R$), and dimensionless tidal deformability ($\Lambda$) to infer the


equation of state (EoS) combining electromagnetic and gravitational wave (GW)


observations. We present a new method to parameterize $R(M)$ and $\Lambda(M)$


relations, which approximate the candidate EoSs with accuracy better than 5\%


for all masses and span a broad region of $M-R-\Lambda$ plane. Using this


method we combine the $M-\Lambda$ measurement from GW170817 and GW190425, and


simultaneous $M-R$ measurement of PSR J0030+0451 and PSR J0740+6620 to place


joint constraints on NS properties. At 90 \% confidence, we infer


$R_{1.4}=12.05_{-0.87}^{+0.98}$ km and $\Lambda_{1.4}=372_{-150}^{+220}$ for a


$1.4 M_{\odot}$ NS, and $R_{2.08}=12.65_{-1.46}^{+1.36}$ km for a $2.08


M_{\odot}$ NS. Furthermore, we use the inferred values of the maximum mass of a


nonrotating NS $M_{\rm max}=2.52_{-0.29}^{+0.33} M_{\odot}$ to investigate the


nature of the secondary objects in three potential neutron star-black hole


merger (NSBH) system.