Compact stars with dark matter induced anisotropy in complexity-free background and effect of dark matter on GW echoes

Abstract

In this work we consider the vanishing complexity factor scenario [Phys Rev D 97: 044010, 2018] which has opened up a whole new way of generating solutions to the Einstein field equations for the spherically symmetric structure of celestial bodies. By using this very rare condition on the system of two metric potentials [Eur Phys J C 82:706, 2022], viz. gtt and grr, we make reduce it to a uni-metric potential system satisfying all physical conditions. Along with this, we further have considered that the spacetime is deformed by dark matter (DM) content in DM halos resulting into perturbations in the gtt and grr metric potentials. This DM deformation is mathematically done by the complete geometric decoupling (CGD) method where the decoupling parameter β decides the amount of DM content. In connection to the claimed post-merger object in the GW170817 event we have argued that if these compact stars were in galactic DM halos with the assumption that the radius remains the same, the compactness factor can grow within the range 1/3 to 4/9 and therefore can generate GW echoes. Additionally, we have presented effect of β on the generation of GW echoes in accordance with the observational constraints related to the compact stars GW190814, PSR J0740+6620, PSR J1614-2230, Cen X-3 and LMC X-4.

Anisotropic compact star in linear f(Q)-action

“…This technique was subsequently refined by Harrison et al [105] and Zel'dovich-Novikov [95] for the specific case of a polytropic equation of state, where the radial pressure is described by the equation P r = Kϵ Γr . The stability of the stellar configuration under a minor radial oscillation is contingent upon the positivity of the characteristic frequency (σ 2 > 0), but only when considering a value of Γ r greater than 4/3 and the final form of the characteristic frequency σ 2 [106],…”

Anisotropic stellar structures admitting Karmakar condition in f(R, φ, χ) theory

“…This approach enabled them to further explore the characteristics and viability of compact structures in a different gravitational framework, expanding our understanding of these intriguing astrophysical objects. They also employed the vanishing complexity factor to assess the viability of compact spherical structures [36].…”

Anisotropic stellar evolution and exotic matter

“…Bower and Liang [18] conducted an analysis of locally anisotropic pressure distributions in spherically symmetric matter and found that pressure anisotropy has a significant impact on the parameters governing the hydrostatic equilibrium of celestial systems. Maurya and his team [19,20] examined compact stars by considering anisotropic pressure profiles. The outcomes of their study are valuable for assessing the stability of compact objects.…”