Radial oscillations of quark stars in light of current astrophysical constraints: A comparative study

Abstract

We investigate the structural and oscillatory properties of isotropic strange quark stars within General Relativity, focusing on three physically motivated equations of state: the color flavor locked (CFL) phase, an interacting quark matter model, and a linear (causal) equation of state. By numerically solving the Tolman Oppenheimer Volkoff and radial perturbation equations, we construct equilibrium stellar sequences and compute oscillation spectra across three representative masses (0.77, 1.40, and 2.00 solar masses). Our analysis is focused on two diagnostics: (i) mass to radius profiles and (ii) radial mode eigenfrequencies with large frequency separations. We compare theoretical predictions against multimessenger constraints from NICER X ray timing of key pulsars, the massive pulsars at two solar masses, and the low mass compact object in HESS J1731--347. All three equations of state yield maximum masses exceeding 2 solar masses with canonical mass radii of (10--12) km, satisfying current observational bounds. Fundamental mode frequencies span (4--7) kHz, with asymptotic large separations differing among the models. These elevated frequencies lie within the detection band of current and next generation gravitational-wave observatories, offering potential asteroseismic signatures for distinguishing strange quark stars from hadronic neutron stars in post merger emission. Our results demonstrate that self bound quark matter naturally accommodates the sub solar mass configuration of HESS J1731--347, reinforcing the viability of strange quark star interpretations.