Neutrino magnetic moment portal and supernovae: New constraints and multimessenger opportunities

We scrutinize the hypothesis that gauge singlet fermions -- sterile neutrinos interact with Standard Model particles through transition magnetic moment portal. These interactions lead to production of in supernovae followed by their decay into photons and active which can be detected at $\gamma$-ray telescopes neutrino detectors, respectively. find non-observation from sterile-neutrino associated SN1987A yields strongest constraints date on magnetic-moment-coupled if masses are inside a $0.1-100$ MeV window. Assuming near-future galactic supernova explosion, we estimate sensitivity several present experiments, including Fermi-LAT, e-ASTROGAM, DUNE, Hyper-Kamiokande, neutrinos. also study diffuse photon fluxes produced magnetic-moment coupled all past explosions absence these daughters for $1-100$ keV