Constraining the equation of state of dense nuclear matter using thermal emission of neutron stars

Abstract

In this work, the equation of state (EoS) of the dense matter in the core of neutron stars (NSs) is based on a recently proposed meta-modeling of nuclear matter composed of nucleons, which can be parametrized by empirical quantities such as the energy density at saturation density or the nuclear incompressibility modulus. We use a set of recent observations of the thermal emission of seven NSs in quiescent low-mass X-ray binaries (qLMXBs) in order to find some constraints on the parameters of the meta-model, and thus on the nuclear EoS. This is done in a Bayesian statistical framework using Markov Chain Monte Carlo (MCMC) methods, to perform a simultaneous analysis over the seven sources. For the first time, the theoretical modeling of the EoS is directly implemented in the data analysis. We obtain constraints on the slope of the symmetry energy, MeV, and give the first estimation of its curvature, MeV, and on the isoscalar skewness parameter, MeV. Radii of about 12 km are preferred with a good fit statistic, yielding a nuclear EoS that is consistent with observational data and recent gravitational waves signals from NSs coalescence.