A Bayesian Approach Study of Hybrid Neutron Stars

TL;DR

This study uses Bayesian analysis of astronomical data to investigate the presence of quark matter in neutron stars, suggesting phase transitions at certain densities and the possibility of large quark cores within hybrid stars.

Contribution

It introduces a Bayesian framework to constrain quark matter phase transitions in neutron stars using observational data and specific hadronic and quark matter models.

Findings

Phase transition may occur below 2.0 times nuclear saturation density.

Hybrid neutron stars could have quark cores exceeding 80% of their total size.

Bayesian analysis constrains model parameters related to quark matter presence.

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.