Strange magnetars admixed with fermionic dark matter

Abstract

We discuss strange stars admixed with fermionic dark matter in the presence of a strong magnetic field using the two-fluid Tolman-Oppenheimer-Volkov equations. We describe strange quark matter using the MIT bag model and consider magnetic fields in the range $\sim 10^{17}-10^{18}$ G. For the fermionic dark matter, we consider the cases of free particles and strongly self-interacting particles, with dark fermion masses $m=5, 100, 500$ GeV. We discuss the effects of dark matter and a strong magnetic field on the masses and radii of the stars, as well as on its tidal deformability. Even though strong magnetic fields contribute to decreasing the total mass of the star, they attenuate the rate of decrease in the maximum mass brought about by increasing the dark matter fraction in the admixed system. The most intensely affected observable, however, is the tidal deformability, with variations on the range of $70\%-90\%$ for reasonable values of the magnetic field or dark matter central energy density.