SN 2011ht: Confirming a Class of Interacting Supernovae with Plateau Light Curves (Type IIn-P)

Understand

We present photometry and spectroscopy of the Type IIn supernova (SN) 2011ht, identified previously as a SN impostor.

• The light curve exhibits an abrupt transition from a well-defined ~120 day plateau to a steep bolometric decline.
• Leading up to peak brightness, a hot emission-line spectrum exhibits signs of interaction with circumstellar material (CSM), in the form of relatively narrow P-Cygni features of H I and He I superimposed on broad Lorentzian wings.
• For the remainder of the plateau phase the spectrum exhibits strengthening P-Cygni profiles of Fe II, Ca II, and H-alpha.