Radial Oscillations of Dark Matter admixed Neutron Stars

TL;DR

This paper studies how dark matter influences neutron star properties, including mass, radius, and oscillation frequencies, revealing that dark matter softens the EOS and increases pulsation frequencies, with implications for star stability.

Contribution

It introduces a detailed analysis of dark matter effects on neutron star oscillations and stability using the relativistic mean-field model and IOPB-I EOS, highlighting the impact of dark matter on star properties.

Findings

Dark matter softens the EOS, reducing maximum mass and radius.

Presence of dark matter increases pulsation frequencies.

Fundamental mode frequency linearly relates to dark matter Fermi momentum.

Abstract

Within the relativistic mean-field model, we investigate the properties of dark matter (DM) admixed neutron stars, considering non-rotating objects made of isotropic matter. We adopt the IOPB-I hadronic equation of state (EOS) by assuming that the fermionic DM within super-symmetric models has already been accreted inside the neutron star (NS). The impact of DM on the mass-radius relationships and the radial oscillations of pulsating DM admixed neutron stars (with and without the crust) are explored. It is observed that the presence of DM softens the EOS, which in turn lowers the maximum mass and its corresponding radius. Moreover, adding DM results in higher frequencies of pulsating objects and hence we show the linearity of fundamental mode frequency of canonical NS with DM Fermi momentum. We also investigate the profile of eigenfunctions solving the Sturm-Liouville boundary value problem, and verify its validity. Further, we study the stability of NSs considering the fundamental mode frequency variation with the mass of the star, and verify the stability criterion $\partial M/\partial\rho_c > 0$. Finally, the effect of the crust on the large frequency separation for different DM Fermi momenta is shown as well.