Implication of multimessenger observations on the relativistic mean-field equation of state of dense nuclear matter and skin thickness of nuclei

TL;DR

This study constrains the nuclear matter equation of state using multimessenger astrophysical data and nuclear experiments, revealing implications for neutron star properties and nuclear skin thicknesses.

Contribution

It combines multimessenger observations with Bayesian analysis to tightly constrain the RMF model parameters and neutron star characteristics, highlighting the role of the $ ho$-$ ho$ coupling.

Findings

GW170817 and NICER data favor a soft EoS

Radius of 1.4 solar mass neutron star is about 12.5 km

Neutron skin thickness of $^{48}$Ca matches CREX, but $^{208}$Pb remains in tension

Abstract

The composition and properties of infinite nuclear matter under extreme conditions of temperature and pressure remain incompletely understood. In this work, we constrain the equation of state (EoS) of nuclear matter - constructed within the framework of the Relativistic Mean Field (RMF) model - by combining results from chiral effective field theory and multimessenger observations of neutron stars. Using the saturation properties of nuclear matter, we generate a wide ensemble of EoS, which are subsequently constrained within a Bayesian framework. The resulting posterior distributions provide tight bounds on both the saturation parameters and the coupling constants of the RMF model. Our results indicate that the GW170817 event and the latest NICER observation favor a relatively soft EoS, leading to lower crust-core transition densities and thinner neutron star crusts. The radius of a $1.4\,M_\odot$ neutron star is tightly constrained to $12.508_{-0.241}^{+0.257}$ km, while the maximum mass reaches $2.174_{-0.123}^{+0.174}\,M_\odot$. Furthermore, our analysis reveals that the $\omega$-$\rho$ coupling, which governs the density dependence of the symmetry energy, becomes increasingly significant under successive astrophysical constraints. Finally, the predicted neutron skin thickness of $^{48}$Ca agrees well with the CREX measurement, whereas that of $^{208}$Pb remains in tension with PREX-II. In contrast to earlier studies, we do not observe a clear correlation between the neutron skin thickness of $^{208}$Pb and the symmetry energy slope parameter $L$.