Solar γ rays as a complementary probe of dark matter

We show that observations of solar γ rays offer a novel probe of dark matter in scenarios where interactions with the visible sector proceed via a long-lived mediator. As a proof of principle, we demonstrate that there exists a class of models which yield solar γ-ray fluxes observable with the next generation of γ-ray telescopes, while being allowed by a variety of current experimental constraints. The parameter space allowed by big bang nucleosynthesis and beam dump experiments naturally leads to mediator lifetimes sufficient to produce observable solar γ-ray signals. The model allows for solar γ-ray fluxes up to orders of magnitude larger compared to dwarf spheroidal galaxies, without reaching equilibrium between dark matter annihilation and capture rate. Our results suggest that solar γ-ray observations are complementary, and in some cases superior, to existing and future dark matter detection efforts.