Quark-hybrid matter in the cores of massive neutron stars

TL;DR

This study uses a nonlocal SU(3) Nambu-Jona Lasinio model to suggest that massive neutron stars can contain quark-hybrid matter cores, with pure quark matter only in unstable configurations, impacting our understanding of their internal composition.

Contribution

It introduces a nonlocal model to demonstrate the possible existence of quark-hybrid matter in neutron star cores up to 2.1 solar masses, challenging previous assumptions about pure quark matter presence.

Findings

Massive neutron stars (~2.1 M_Sun) can host quark-hybrid cores.

Pure quark matter appears only in unstable neutron star configurations.

Neutron star radii are consistent with 12-13 km in these models.

Abstract

Using a nonlocal extension of the SU(3) Nambu-Jona Lasinio model, which reproduces several of the key features of Quantum Chromodynamics, we show that mixed phases of deconfined quarks and confined hadrons (quark-hybrid matter) may exist in the cores of neutron stars as massive as around 2.1 M_Sun. The radii of these objects are found to be in the canonical range of $\sim 12-13$ km. According to our study, the transition to pure quark matter does not occur in stable neutron stars, but is shifted to neutron stars which are unstable against radial oscillations. The implications of our study for the recently discovered, massive neutron star PSR J1614-2230, whose gravitational mass is $1.97 \pm 0.04 M_Sun$, are that this neutron star may contain an extended region of quark-hybrid matter at it center, but no pure quark matter.