Dark Matter-admixed Rotating White Dwarfs as Peculiar Compact Objects

Abstract: The discoveries of anomalous compact objects challenge our understanding of the standard theory of stellar structures and evolution. They serve as an excellent laboratory to search for new physics. Earlier studies on spherically symmetric dark matter-admixed compact stars could explain a handful of anomalies. In this paper, we investigate the observational signatures of dark matter (DM)-admixed rotating white dwarfs and make connections to observed peculiar white dwarfs. We compute the equilibrium structures of DM-admixed rotating white dwarfs using a self-consistent, two-fluid method, with the DM component being a non-rotating degenerate fermi gas. We find that the admixture of DM in rotating white dwarfs could: (1) account for some peculiar white dwarfs that do not follow their usual mass-radius relation, (2) allow the existence of stable, rapid-rotating white dwarfs that are free from thermonuclear runaway, which could explain some anomalous x-ray pulsars/soft gamma-ray repeaters, and (3) produce universal $I$ (moment of inertia)-Love (tidal Love number)-$Q$ (quadrupole moment) relations that span bands above those without DM admixture, thus providing an indirect way to search for DM in white dwarfs through gravitational-wave detection. DM-admixed rotating white dwarfs can account for some peculiar compact objects. Our results suggest a systematic approach to account for unusual compact objects that could be discovered by upcoming surveys.