Uniformly rotating, axisymmetric and triaxial quark stars in general relativity

TL;DR

This paper models uniformly rotating, axisymmetric, and triaxial quark stars in general relativity, extending computational methods to include new equations of state and analyzing their stability and gravitational wave emissions.

Contribution

The study introduces an extended COCAL code for rotating quark stars with finite surface density and new EOSs, including a stiff EOS supporting higher masses.

Findings

The new code achieves convergence for various compactness levels.

Quark stars can reach masses up to 3.3 solar masses with the new EOS.

Estimated gravitational wave signals from quark stars are discussed.

Abstract

Quasi-equilibrium models of uniformly rotating axisymmetric and triaxial quark stars are computed in general relativistic gravity scenario. The Isenberg-Wilson-Mathews (IWM) formulation is employed and the Compact Object CALculator (COCAL) code is extended to treat rotating stars with finite surface density and new equations of state (EOSs). Besides the MIT bag model for quark matter which is composed of de-confined quarks, we examine a new EOS proposed by Lai and Xu that is based on quark clustering and results in a stiff EOS that can support masses up to $3.3M_\odot$ in the case we considered. We perform convergence tests for our new code to evaluate the effect of finite surface density in the accuracy of our solutions and construct sequences of solutions for both small and high compactness. The onset of secular instability due to viscous dissipation is identified and possible implications are discussed. An estimate of the gravitational wave amplitude and luminosity based on quadrupole formulas is presented and comparison with neutron stars is discussed.