Semi Universal relation to understand matter properties at neutron star interiors

TL;DR

This paper introduces semi-empirical parameters to quantify quark matter in neutron star interiors, revealing semi-universal relations across equations of state and implications for star stability and collapse.

Contribution

It defines new semi-empirical parameters that relate quark content to neutron star properties and demonstrates their semi-universal behavior across different equations of state.

Findings

A constant shift in mass-radius relation across EoS

Quark content influences tidal deformability and compactness

Increased quark content correlates with higher collapse likelihood

Abstract

The occurrence of quark matter at the center of neutron stars is still in debate. This study defines some semi-empirical parameters that quantify the occurrence and the amount of quark matter at star interiors. These parameters show semi-universal relations across all the EoS. One parameter depends on the shifting of the keplerian mass-radius curve from the static one and shows it is a constant across all EoS. The Z-parameter shows how tidal deformability depends on the quark content of the star and the stiffness of the EoS. The quark content of the star also affects the compactness of the star, and its dependence is almost universal. The empirical parameter gives a bound on the quark content of the star and shows that if the amount of the quark content increases, the stars are likely to collapse into a black hole. It is seen that the change in the mass and radius after PT is linearly proportional to the mass of the parent NS. Given a hadronic EoS, bag constant, and quark coupling constant, one can have a critical mass of the neutron star and the maximum mass of the hybrid star for phase transition without any baryonic mass loss.