Rotational enhancement and stability of protoquark stars during thermal evolution

TL;DR

This study systematically investigates how rapid rotation and thermal evolution influence the stability, structure, and observable properties of protoquark stars, highlighting their potential signatures in multimessenger astrophysics.

Contribution

It introduces the first detailed analysis of rotating protoquark stars with isentropic EOS within the DDQM framework, emphasizing the effects of rotation and thermal evolution on their stability and observables.

Findings

Rotation increases maximum stable mass by up to 40%

Protoquark stars have larger radii and moments of inertia than hadronic stars

Stars exhibit peak properties during lepton-rich stages and decrease as they cool

Abstract

We present the first systematic study of rigidly rotating protoquark stars based on isentropic equations of state (EOS) within the density-dependent quark mass (DDQM) framework. Using a quasi-static equilibrium approach, we follow the Kelvin--Helmholtz evolution from hot, lepton-rich matter to a cold, catalyzed quark star. Rotation substantially enhances the maximum stable mass (by up to $\sim 40\%$), equatorial radius, and key rotational observables, with the ratio of rotational kinetic to gravitational potential energy, $T_{\rm kin}/|W|$, reaching $0.18$--$0.19$ near the Keplerian limit, indicating a heightened susceptibility to gravitational-wave--emitting instabilities. Thermal evolution introduces a clear ordering: all stellar properties peak during the lepton-rich stages and decrease monotonically as the star cools. Compared to hadronic stars, rotating protoquark stars exhibit larger radii, higher moments of inertia, and stronger quadrupolar deformation, producing a distinct signature in the mass--radius--spin plane that can accommodate objects such as HESS~J1731--347 and PSR~J0740+6620. These results demonstrate that future multimessenger observations must account for both thermal history and rotation to robustly identify quark matter in compact stars.