Constraints on the hybrid equation of state with a crossover hadron-quark phase transition in the light of GW170817

TL;DR

This study constrains hybrid neutron star equations of state using GW170817 data, suggesting the possible existence of hybrid stars with a crossover phase and mixed cores, based on a three-window modeling approach.

Contribution

It introduces a constrained hybrid EOS model combining hadronic and quark matter, informed by GW170817 data, and explores the nature of hybrid stars with crossover transitions.

Findings

Hybrid EOS parameters are well constrained by GW170817 data.

Hybrid stars likely have a mixed-phase core rather than a pure quark core.

The study identifies possible hybrid star configurations consistent with observational constraints.

Abstract

In this paper, we use the recent updated source properties of GW170817 to constrain the hybrid equation of state (EOS) constructed by a three-window modeling between the hadronic EOS and quark EOS. Specifically, the hadronic EOS is described by NL3$\omega\rho$ model whose corresponding pure neutron star (NS) is already excluded by the constraint of tidal deformability (TD) from GW170817, and the quark EOS is calculated with 2+1 flavors Nambu-Jona-Lasinio (NJL) model. We also consider other four constraints on the hybrid EOS. As a result, we find the parameter set ($B^{\frac{1}{4}}, \tilde{\mu}, \Gamma$) can be well constrained, indicating the possible existence of the hybrid star (HS) with a crossover inside. The type of the two stars in the binary system for nine representative hybrid EOSs is shown in this paper too. Furthermore, the HSs restricted by five constraints do not suggest a pure quark core but a mixed-phase in center.