New class of high-energy transients from crashes of supernova ejecta with massive circumstellar material shells

A new class of core-collapse supernovae (SNe) has been discovered in recent years by optical/infrared surveys; these SNe suggest the presence of one or more extremely dense (∼105^-11 cm^-3) shells of circumstellar material (CSM) on 102^-4AU scales. We consider the collisions of the SN ejecta with these massive CSM shells as potential cosmic-ray (CR) accelerators. If ∼10% of the SN energy goes into CRs, multi-TeV neutrinos and/or GeV-TeV gamma rays almost simultaneous with the optical/infrared light curves are detectable for SNe at 20-30Mpc. A new type of coordinated multimessenger search for such transients of duration ∼1-10 months is required; these may give important clues to the physical origin of such SNe and to CR acceleration mechanisms.