Exploring the Dark Frontier: White Dwarf-Based Constraints on Light Dark Matter

Abstract: In the vast expanse of our galaxy, white dwarfs (WDs) are natural sentinels, capturing the enigmatic dark matter (DM) particles that incessantly traverse their interiors. These celestial bodies provide a unique vantage point for probing interactions between DM particles and their constituents-nuclei or electrons-should such interactions exist. The captured DM particles may accumulate, undergo mutual annihilation, or be evaporated by the WD's own nuclei or electrons, thereby perturbing the standard cooling sequence predicted by stellar evolution theory. This letter reports pioneering constraints on DM-electron interactions derived from an in-depth analysis of four pulsating WDs. By leveraging the period variation rates of their pulsation modes, we delineate the following constraints: for a form factor $F(q) = 1$, in the DM mass range $20 \mathrm{MeV}/c^{2} \lesssim m_{\chi} \lesssim 80 \mathrm{MeV}/c^{2}$ with a cross-section limit of $\sigma_{\chi,e} \lesssim 10^{-56} \mathrm{cm}^{2}$; for a form factor $F(q) = (\alpha m_{e})^{2}/q^{2}$, in a the DM mass range $20\mathrm{MeV}/c^{2} \lesssim m_{\chi} \lesssim 70 \mathrm{MeV}/c^{2}$ with a limit of $\sigma_{\chi,e} \lesssim 10^{-52} \mathrm{cm}^{2}$. These newly established constraints surpass current direct detection experiments by over fifteen orders of magnitude, forging a path into the uncharted territories of the DM parameter space. This work not only advances our understanding of light dark matter-electron interactions but also exemplifies the potential of WDs as important astrophysical laboratories for probing the elusive nature of DM.