Hydrogenless Superluminous Supernova PTF12dam in the Model of an Explosion inside an Extended Envelope

A model of a supernova explosion inside a dense extended hydrogenless envelope is proposed to explain the properties of the light curve for one of the superluminous supernovae PTF12dam. It is argued in the literature that the flux of this supernova rises too fast to be explained by the explosion model due to the instability associated with the electron-positron pair production (pair-instability supernova, PISNe), but it is well described by the models with energy input by a magnetar. We show that the PTF12dam-type supernovae can be explained without a magnetar in a model with a radiative shock in a dense circumstellar envelope that does not require an excessively large explosion energy.