A Bayesian Approach Study of Hybrid Neutron Stars

Abstract

In this work, we explore how astronomical observations (specifically measurements of masses, radii, and tidal deformabilities) can constrain the presence of quark matter inside neutron stars, namely the phase transition from nuclear matter to deconfined quark matter. Our approach employs Bayesian analysis to study this phenomenon. Hadronic matter is modeled using the relativistic mean-field (RMF) approximation, for which we have selected two parameter sets: \(NL3^{*}\omega\rho\), representing hadronic matter with nucleons only, and $EL3\omega\rho$ with nucleons only and $EL3\omega\rho Y$, which includes hyperons. On the other hand deconfined quark matter is modeled using the vector-MIT bag model. For our purpose, the phase transition is implemented using the Maxwell construction. Bayesian inference is performed by tuning three parameters: the bag constant (i.e. $B^{1/4}$), the vector coupling constant \(\left(G_{v}\right)\), and the Dirac sea contribution ($b_{4}$). We found that a phase transition could exist at densities below \(2.0\,n_{0}\) for both the $EL3\omega\rho - EL3\omega\rho Y $ and $NL3^{*}\omega\rho$ parametrizations. As a consequence, our results also indicate that a hybrid neutron star could have a large quark core that comprises more than \(80\%\) of its size.