Constraints on the Dense Matter Equation of State and Neutron Star Properties from NICER’s Mass–Radius Estimate of PSR J0740+6620 and Multimessenger Observations

In recent years our understanding of the dense matter equation state (EOS) neutron stars has significantly improved by analyzing multimessenger data from radio/X-ray pulsars, gravitational wave events, and nuclear physics constraints. Here we study additional impact on EOS jointly estimated mass radius PSR J0740+6620, presented in Riley et al. a combined set X-ray telescopes NICER XMM-Newton. We employ two different high-density parameterizations: piecewise-polytropic (PP) model based speed sound star (CS). At densities these are connected to microscopic calculations chiral effective field theory (EFT) interactions. addition new for this heavy star, separately constraints radio timing measurement events binary GW190425 GW170817, latter associated kilonova AT2017gfo. By combining all these, mass–radius estimate J0030+0451, find 1.4 M⊙ be constrained 95% credible ranges (PP model) (CS model). addition, explore EFT show that results provide tight pressure at around twice saturation density, which shows power observations constrain interactions intermediate densities.