Radial oscillations of strange quark stars admixed with condensed dark matter

TL;DR

This study analyzes how condensed dark matter influences the radial oscillation modes of strange quark stars, revealing that dark matter increases mode separation, especially in higher modes, even at low dark matter fractions.

Contribution

It provides the first detailed computation of radial oscillation modes of strange stars with condensed dark matter modeled as a Bose-Einstein condensate.

Findings

Mode separation increases with dark matter content.

Higher order modes are more affected by dark matter.

Effects are significant even with 5% dark matter fraction.

Abstract

We compute the 20 lowest frequency radial oscillation modes of strange stars admixed with condensed dark matter. We assume a self-interacting bosonic dark matter, and we model dark matter inside the star as a Bose-Einstein condensate. In this case the equation of state is a polytropic one with index $1+1/n=2$ and a constant $K$ that is computed in terms of the mass of the dark matter particle and the scattering length. Assuming a mass and a scattering length compatible with current observational bounds for self-interacting dark matter, we have integrated numerically first the Tolman-Oppenheimer-Volkoff equations for the hydrostatic equilibrium, and then the equations for the perturbations $\xi=\Delta r/r$ and $\eta=\Delta P/P$. For a compact object with certain mass and radius we have considered here three cases, namely no dark matter at all and two different dark matter scenarios. Our results show that i) the separation between consecutive modes increases with the amount of dark matter, and ii) the effect is more pronounced for higher order modes. These effects are relevant even for a strange star made of 5\% dark matter.