Supernova progenitor constraints from circumstellar interaction: Type II
  All types of supernovae (SNe), except Type Ia, have been observed to interact with their immediate circumstellar medium (CSM). This interaction can reveal their progenitor's histories, and constrain our ideas about the evolution of massive stars. As examples of the latest progress in this areas, we present some new results on two SNe: a 3D picture of the triple-ring nebula around SN 1987A, and observations of the less well-known but rather intriguing SN 1994W. In the process we introduce Type IIn supernovae (SN IIn; Schlegel 1990) as an important new probe of massive star evolution. 
Robert J. Cumming and Peter Lundqvist (Stockholm Observatory)