Milky Way White Dwarfs as Sub-GeV to Multi-TeV Dark Matter Detectors

TL;DR

This paper demonstrates that Milky Way white dwarfs can serve as highly sensitive detectors for a wide range of dark matter particles, providing constraints that surpass existing direct detection methods.

Contribution

It introduces a novel method of using white dwarf gamma-ray data to set new, stronger limits on dark matter interactions across a broad mass range, improving previous capture calculations.

Findings

White dwarfs provide constraints on dark matter cross sections down to 10^{-45} cm^2.

White dwarf constraints surpass traditional direct detection limits in most of the sub-GeV to multi-TeV range.

Refined capture rate calculations account for low-temperature nuclei distributions, reducing previous estimates.

Abstract

We show that Milky Way white dwarfs are excellent targets for dark matter (DM) detection. Using Fermi and H.E.S.S. Galactic center gamma-ray data, we investigate sensitivity to DM annihilating within white dwarfs into long-lived or boosted mediators and producing detectable gamma rays. Depending on the Galactic DM distribution, we set new constraints on the spin-independent scattering cross section down to $10^{-45}-10^{-41}$ cm$^2$ in the sub-GeV DM mass range, which is multiple orders of magnitude stronger than existing limits. For a generalized NFW DM profile, we find that our white dwarf constraints exceed spin-independent direct detection limits across most of the sub-GeV to multi-TeV DM mass range, achieving sensitivities as low as about $10^{-46}$ cm$^2$. In addition, we improve earlier versions of the DM capture calculation in white dwarfs, by including the low-temperature distribution of nuclei when the white dwarf approaches crystallization. This yields smaller capture rates than previously calculated by a factor of a few up to two orders of magnitude, depending on white dwarf size and the astrophysical system.