SN 2012aa: A transient between Type Ibc core-collapse and superluminous supernovae

Context. Research on supernovae (SNe) over the past decade has confirmed that there is a distinct class of events which are much more luminous (by ~2 mag) than canonical core-collapse SNe (CCSNe). These events with visual peak magnitudes ≲–21 are called superluminous SNe (SLSNe). The mechanism that powers the light curves of SLSNe is still not well understood. The proposed scenarios are circumstellar interaction, the emergence of a magnetar after core collapse, or disruption of a massive star through pair production.