Cold Quark-Gluon Plasma EOS Applied to a Magnetically Deformed Quark Star with an Anomalous Magnetic Moment

TL;DR

This paper models magnetically deformed quark stars using a QCD-based EOS with an anomalous magnetic moment, revealing how shape and magnetic effects influence star mass and radius without collapsing into black holes.

Contribution

It introduces a novel approach combining shape deformation and AMM effects into the EOS and TOV equations for quark stars, providing new insights into their maximum mass and structure.

Findings

Maximum mass range: 2.3-2.7 solar masses

Shape and magnetic effects increase mass and reduce radius

Consistent with high-mass magnetars and gravitational wave observations

Abstract

We consider a QCD cold plasma motivated Equation of State (EOS) to examine the impact of an Anomalous Magnetic Moment (AMM) coupling and small shape deformations for static oblate and prolate core shapes of quark stars. Using the Foga\c{c}a QCD motivated EOS which shifts from the high temperature low chemical potential quark gluon plasma environment to the low temperature high chemical potential quark stellar core environment we consider the impact of an AMM coupling with a metric induced shape deformation parameter in the TOV equations. The EOS is developed using a hard gluon and soft gluon decomposition of the gluon field tensor using a mean field effective mass for the gluons. The AMM is considered using the Dirac spin tensor coupled to the EM field tensor with quark flavor based magnetic moments. The shape parameter is introduced in a metric ansatz that represents oblate and prolate static stellar cores for modified TOV equations. These equations are numerically solved for the final mass and radius states representing the core collapse of a massive star with a phase transition leading to an unbound quark-gluon plasma. We find that the combined shape parameter and AMM effects can alter the coupled EOS-TOV equations resulting in an increase in the final mass and a decrease in the final equatorial radius without collapsing the core into a black hole and without violating causality constraints, we find maximum mass values in the range: 2.3 Solar Masses < M < 2.7 Solar Masses. These states are consistent with some astrophysical high mass magnetar/pulsar and gravity wave systems which may provide evidence for a core that has undergone a quark-gluon phase transition such as PSR 0943+10 and the secondary from the GW 190814 event.