Probing geometrically perturbed strange stars with minimal decoupling using millisecond pulsar timing observations

TL;DR

This paper models anisotropic strange stars using gravitational decoupling and minimal geometric deformation, fitting high-mass pulsar data and analyzing stability and compactness with perturbations.

Contribution

It introduces a novel anisotropic strange star model with minimal geometric deformation, constrained by pulsar observations, and explores effects of perturbations on stability and structure.

Findings

Maximum mass reaches about 2.28 solar masses.

Anisotropy increases outward, supporting higher compactness.

Perturbations allow stable ultra-compact star configurations.

Abstract

We construct a gravitationally decoupled anisotropic strange star model using the minimal geometric deformation approach with a MIT bag equation of state and an additional source sector controlled by a deformation parameter $\beta$ and a radial perturbation scale $\Psi$ through $g(r)=\sin(\Psi r^{2})$. The resulting Einstein system is consistently split into seed and $\theta$-sectors and matched to an exterior Schwarzschild geometry. The model is constrained by high-mass pulsars: PSR J0740+6620 $(2.08\pm0.07\,M_\odot)$, PSR J1810+1744 $(2.13\pm0.04\,M_\odot)$, PSR J1959+2048 $(2.18\pm0.09\,M_\odot)$, and PSR J2215+5135 $(2.28^{+0.10}_{-0.09}\,M_\odot)$. It reproduces these objects with predicted radii $R \approx 11.3$--$12.9$ km. The maximum mass reaches $M_{\max} \approx 2.28\,M_\odot$ for $\beta = 3\times 10^{-3}$ and $\Psi \approx 0.03\,\text{km}^{-2}$, while for $\beta = 10^{-3}$ the configuration yields $M_{\max} \approx 2.12\,M_\odot$ with $R \approx 12.2$ km. The central density lies in $\rho_c \approx (2.4$--$3.1)\times 10^{-4}\,\text{km}^{-2}$, decreasing smoothly to $\rho_s \approx 2.0\times 10^{-4}\,\text{km}^{-2}$. The anisotropy increases from zero at the center to $\Delta \approx (0.25$--$0.45)\times 10^{-4}\,\text{km}^{-2}$ near the surface, generating additional outward support that enhances compactness by $\sim 15\%$. The compactness parameter spans $C \approx 0.17$--$0.22$, safely below the Buchdahl limit, while the surface redshift reaches $z_s \approx 0.25$--$0.38$. The condition $dM/d\rho_c > 0$ is satisfied throughout, confirming dynamical stability. Overall, $\beta$ enhances the maximum mass by up to $\sim 15\%$, while $\Psi$ introduces controlled oscillatory structure without violating observational constraints, producing stable ultra-compact stars consistent with current pulsar data.