Hybrid Stars in the Framework of NJL Models

Gustavo A Contrera,I F Ranea-Sandoval,Milva Orsaria,Fridolin Weber

doi:10.1142/s2010194517600266

Abstract

We compute models for the equation of state (EoS) of the matter in the cores of hybrid stars. Hadronic matter is treated in the non-linear relativistic mean-field approximation, and quark matter is modeled by three-flavor local and non-local Nambu−Jona-Lasinio (NJL) models with repulsive vector interactions. The transition from hadronic to quark matter is constructed by considering either a soft phase transition (Gibbs construction) or a sharp phase transition (Maxwell construction). We find that high-mass neutron stars with masses up to [Formula: see text] may contain a mixed phase with hadrons and quarks in their cores, if global charge conservation is imposed via the Gibbs conditions. However, if the Maxwell conditions is considered, the appearance of a pure quark matter core either destabilizes the star immediately (commonly for non-local NJL models) or leads to a very short hybrid star branch in the mass-radius relation (generally for local NJL models).

Highlights

The question of whether or not quark matter exists in neutron stars has received renewed interest (see Refs.,[1,2,3] and references therein) by the discovery of the two massive neutron stars (NS) J1614–2230 (1.97±0.04M (see Ref.4), recently updated to 1.928 ± 0.017M (see Ref.5) and J0348+0432 (2.01 ± 0.04M (see Ref.6))
The question of whether or not quark matter exists in neutron stars has received renewed interest by the discovery of the two massive neutron stars (NS) J1614–2230 (1.97±0.04M, recently updated to 1.928 ± 0.017M and J0348+0432 (2.01 ± 0.04M)
Just as for the hyperon content of NS, strangeness is not conserved on macroscopic time scales, which allows them to convert confined hadronic matter to three-flavor quark matter until equilibrium brings this process to a halt

Summary

Introduction

The question of whether or not quark matter exists in neutron stars has received renewed interest (see Refs.,[1,2,3] and references therein) by the discovery of the two massive neutron stars (NS) J1614–2230 (1.97±0.04M (see Ref.4), recently updated to 1.928 ± 0.017M (see Ref.5) and J0348+0432 (2.01 ± 0.04M (see Ref.6)). It has been shown[11,12,13] that the appearance of a mixed phase of quarks and hadrons in NS is favored when the value of the surface tension between nuclear matter and quark matter is lower than σ ∼ 40 MeV/fm[2 ].

Results

Conclusion