Hunting Sterile Neutrino Dark Matter in the MeV Gap

We investigate the sensitivities of upcoming MeV gamma-ray telescopes to sterile neutrino dark matter in the mass range $(0.2-100)\mathrm{M}\mathrm{e}\mathrm{V}$. Sterile neutrinos in this regime can produce observable photon signals through radiative two-body decays and three-body decays with final-state radiation. We perform a Fisher forecasting analysis incorporating realistic astrophysical background modeling and detector response to derive projected constraints on the sterile neutrino decay rate. We find that future MeV instruments can improve existing limits by several orders of magnitude across a wide region of parameter space. Our results highlight the discovery potential of next-generation MeV telescopes in probing sterile neutrino dark matter.