Abstract

Two new kinds of peculiar type II supernovae (SNe) have been observed recently: namely the very luminous type II radio supernovae (RSNe) and the so-called Seyfert 1 imposter. I will show that a simple model of interaction of supernova (SN) ejecta with a high-density homogeneous circumstellar medium (CSM), combining analytic and numerical hydrodynamic simulations together with static photoionization computations, can describe their observed emitted spectrum, optical light curve, X-ray luminosity and emission line widths. I suggest that these two new kinds of SNe are not peculiar type IIs, but are, in fact, the optical or radio manifestation of the same phenomenon, i.e. the interaction of the SN ejecta with a high density CSM.

During the interaction with a high density CSM a young remnant can radiate most of its kinetic energy and outshine the SN event itself; therefore to emphasize the unique aspects associated with this type of event, I suggest calling this group of small, luminous and rapidly evolving remnants, compact supernova remnants (cSNRs).