Indirect signals from solar dark matter annihilation to long-lived right-handed neutrinos

We study indirect detection signals from solar annihilation of dark matter (DM) particles into light right-handed (RH) neutrinos with a mass in a 1-5 GeV range. These RH neutrinos can have a sufficiently long lifetime to allow them to decay outside the Sun, and their delayed decays can result in a signal in gamma rays from the otherwise dark solar direction, and also a neutrino signal that is not suppressed by the interactions with solar medium. We find that the latest Fermi-LAT and IceCube results place limits on the gamma ray and neutrino signals, respectively. Combined photon and neutrino bounds can constrain the spin-independent DM-nucleon elastic scattering cross section better than direct detection experiments for DM masses from 200 GeV up to several TeV. The bounds on spin-dependent scattering are also much tighter than the strongest limits from direct detection experiments.