2020MNRAS.494L..86C

The recent study of the SN 2013fs flash spectrum suggests an enormous explosion energy for SNe IIP, far beyond the possibilities of the neutrino mechanism. The issue of the explosion energy of SN 2013fs is revisited, making use of the effects of the early supernova interaction with the dense circumstellar shell. The velocity of the cold dense shell between reverse and forward shocks is inferred from the analysis of the broad He II 4686 Å on day 2.4. This velocity, alongside other observables, provides us with an alternative energy estimate of ∼1.8 x 10⁵¹ erg for the preferred mass of ∼10 M_☉. The inferred value is within the range of neutrino-driven explosions.