Signs of Circumstellar Interaction in Type IIL Supernovae

Single, hydrogen-rich, core collapse supernovae typically divided into three classes: IIP, with a 100 day plateau following maximum light, IIL, showing a linearly declining light curve following maximum light, and IIn which show narrow emission lines in their spectra. These classifications are indicative of the characteristics of the late stage evolution of the hydrogen envelope of the progenitor star. In general, interaction with circumstellar material is only considered for type IIn supernovae. However, recent hydrodynamic modeling of IIP and IIL supernovae with conventional red supergiant progenitors, has been unable to reproduce their early (~30 days post explosion) light curves without the introduction of circumstellar material. In this scenario, IIL supernovae experience large amounts of mass loss before exploding and are the ideal candidates for understanding whether IIP and IIL supernovae experience interaction with a stellar wind. We test this hypothesis on ASASSN-15oz, a type IIL supernova and the closest type II supernova in 2015. With extensive follow-up in the X-ray, UV, optical, IR, and radio we present our search for signs of interaction, and the mass-loss history indicated by their detection.