Probing Dark Matter Long-lived Mediators with Solar $\gamma$ rays

We show that solar $gamma$-ray observations can provide a complementary probe of Dark Matter in scenarios where the interactions with the Standard Model proceed via long-lived mediators. For illustration we consider a simplified model which provides solar $gamma$-rayfluxes observable with the next generation $gamma$-ray telescopes, while complying with the existing experimental constraints. Our results suggest that solar $gamma$-ray fluxes can be orders of magnitude larger than the ones from the Galactic center, while being subject to low backgrounds.