Tidal Properties of White Dwarfs Admixed with Fermionic Dark Matter

Abstract

This study investigates the impact of fermionic dark matter (DM) on the structural and tidal properties of white dwarfs (WDs). Using a two-fluid general relativistic framework, we model stars with fixed DM mass fractions ($\mathrm{MF}=M_{\mathrm{DM}}/M_{\mathrm{NM}}$), ranging from 0\% to 8\%, with zero representing the no DM scenario. Our results indicate that DM accumulation leads to a significant compactification of the star, reflected in increased surface gravity and compactness. Furthermore, we calculate the second-order tidal Love number $k_2$ and the dimensionless tidal deformability $\Lambda$. For some total mass range, we find that the presence of DM significantly reduces $\Lambda$, suggesting that DM-admixed WDs (DMWDs) are less susceptible to tidal deformations. These structural shifts alter the gravitational wave signatures in binary systems, potentially providing a new window for DM detection with future instruments like LISA.