Impact of PREX-II and combined Radio/NICER/XMM-Newton's mass-radius measurement of PSRJ0740+6620 on the dense matter equation of state

Abstract

In this paper, we discuss the impact of the following laboratory experiments and astrophysical observation of neutron stars (NSs) on its equation of state (EoS): (a) The new measurement of neutron skin thickness of $\rm ^{208} \! Pb$, $R_{\rm skin}^{208} = 0.29 \pm 0.07$ fm by the PREX-II experiment. (b) The mass measurement of PSR J0740+6620 has been slightly revised down by including additional $\sim 1.5$ years of pulsar timing data. As well as the radius measurement of PSR J0740+6620 by joint NICER/XMM-Newton collaboration which has a similar size to PSR J0030+0451. We combine these information using Bayesian statistics along with the previous LIGO/Virgo and NICER observations of NS using a hybrid nuclear+piecewise polytrope (PP) EoS parameterization. Our findings are as follows: (a). Adding PREX-II result yields the value of empirical parameter $L = 69^{+21}_{-19}$ MeV, $R_{\rm skin}^{208} = 0.20_{-0.05}^{+0.05}$ fm, and radius of a $1.4 M_{\odot}$ ($R_{1.4}) = 12.75_{-0.54}^{+ 0.42}$ km at $1 \sigma$ confidence interval (CI). We find these inferred values are mostly dominated by the combined astrophysical observations as the measurement uncertainty in $R_{\rm skin}^{208}$ by PREX-II is much broader. Also, a better measurement of $R_{\rm skin}^{208}$ might have a little effect on the radius of low mass NSs, but for the high masses there will be almost no effect. (b) After adding The revised mass and radius measurement of PSR J0740+6620, we find the inferred radius of NSs is slightly pushed towards the larger values and the uncertainty on the radius of a $2.08 M_{\odot}$ NS is moderately improved.