# Equation of state for hybrid stars with strangeness

## TL;DR

This paper investigates the properties of hybrid neutron stars with strangeness by modeling hadronic and quark matter equations of state, analyzing the effects of hadron-quark coexistence on star characteristics.

## Contribution

It introduces a comprehensive model combining hyperons and quarks with relativistic Hartree-Fock approximation and explores hadron-quark phase transitions in neutron stars.

## Key findings

- Stiff hadronic EoS prevents early quark appearance.
- Hadron-quark coexistence affects mass-radius relations.
- Speed of sound and particle fractions are characterized.

## Abstract

Considering the mass constraint from the resent pulsar observations, we study the properties of neutron stars including hyperons and quarks explicitly. Using the chiral quark-meson coupling model with relativistic Hartree-Fock approximation, the equation of state (EoS) for hadronic matter is calculated by taking into account the strange ($\sigma^{\ast}$ and $\phi$) mesons as well as the light non-strange ($\sigma$, $\omega$, $\vec{\rho}$, and $\vec{\pi}$) mesons in SU(3) flavor symmetry. On the other hand, the EoS for quark matter is constructed with the simple MIT bag or the flavor-SU(3) Nambu-Jona-Lasinio model, and we investigate the effect of the hadron-quark coexistence on the neutron-star properties, imposing smooth crossover or Gibbs criterion for chemical equilibrium. The mass-radius relation of a neutron star, as well as physical quantities such as EoSs, particle fractions, and the speed of sound in matter are presented. We find that, in order to prevent the quark appearance at very low densities, the stiff hadronic EoS should be required under both of the hadron-quark crossover and the first-order phase transition.