Speaker
Description
Dark matter (DM) decay in the Galactic halo injects energetic $e^\pm$ that can inverse-Compton scatter (ICS) solar photons into $\gamma$ rays, producing a diffuse halo of emission around the Sun. We present the first quantitative study of this signal as a probe of decaying DM. Using 15 years of Fermi-LAT solar-halo data, we compute the heliocentric ICS signal and derive limits on the DM lifetime for masses between 10 GeV and 10 TeV. For final states with the hardest spectra, we obtain constraints reaching lifetimes of $10^{27}\,\mathrm{s}$. Solar ICS $\gamma$-rays therefore provide a novel and complementary local probe of decaying DM, systematically distinct from both Galactic diffuse $\gamma$-ray searches and direct charged-particle measurements.