Bayesian analysis of hybrid neutron star EOS constraints within an instantaneous nonlocal chiral quark matter model

TL;DR

This paper uses Bayesian methods to analyze neutron star equations of state, incorporating observational data and a nonlocal chiral quark model to identify conditions for hybrid stars with quark matter cores.

Contribution

It introduces a Bayesian framework for constraining hybrid neutron star equations of state using observational data and a nonlocal chiral quark model, highlighting conditions for phase transition and maximum mass.

Findings

Hybrid stars likely have quark cores at 0.5-0.7 solar masses.

Maximum neutron star mass range is 2.15-2.22 solar masses.

Star radii are between 11.9 and 12.4 km for 1.2-2.0 solar masses.

Abstract

We present a physics-informed Bayesian analysis of equation of state constraints using observational data for masses, radii and tidal deformability of pulsars and a generic class of hybrid neutron star equation of state with color superconducting quark matter on the basis of a recently developed nonlocal chiral quark model. The nuclear matter phase is described within a relativistic density functional model of the DD2 class and the phase transition is obtained by a Maxwell construction. We find the region in the two-dimensional parameter space spanned by the vector meson coupling and the scalar diquark coupling, where three conditions are fulfilled: (1) the Maxwell construction can be performed, \mbox{(2) the maximum} mass of the hybrid neutron star is not smaller than \mbox{2.0 M$_\odot$} and (3) the onset density of the phase transition is not below the nuclear saturation density $n_0=0.15$ fm$^{-3}$. The result of this study shows that the favorable neutron star equation of state has low onset masses for the occurrence of a color superconducting quark matter core between 0.5-0.7 $M_\odot$ and maximum masses in the range 2.15-2.22 $M_\odot$. In the typical mass range of 1.2-2.0 $M_\odot$, the radii of these stars are between 11.9 and 12.4 km, almost independent of the mass. In principle, hybrid stars would allow for larger maximum masses than provided by the hadronic reference equation of state.