Detection of a Massive Dust Shell around the Type II Supernova SN 2002hh

Dust emission from the Type II supernova SN 2002hh in NGC 6946 has been detected at mid-infrared wavelengths by the Spitzer Space Telescope from 590 to 758 days after outburst and confirmed by higher angular resolution Gemini North mid-IR observations. The day 600 5.8-24 μm emission can be fit by a 290 K blackbody having a luminosity of 1.6 × 107 L☉. The minimum emitting radius of 1.1 × 1017 cm is too large for the emitting dust to have been formed in the supernova ejecta. Using radiative transfer models and realistic dust grain parameters, fits to the observed flux distribution could be obtained with an optically thick dust shell having a mass of 0.10-0.15 M☉, corresponding to a total dust+gas mass in excess of 10 M☉, suggesting a massive M supergiant or luminous blue variable precursor to this self-obscured object.