The infrared echo of a type II supernova with a circumstellar dust shell - Applications to SN 1979c and SN 1980k

Merrill (1980) and Telesco et al. (1981) have reported observations according to which supernovae developed a thermal infrared excess about 7-9 months after visual maximum. The two supernovae involved are SN 1979c in NGC 4321 and SN 1980k in NGC 6946. The infrared behavior of these supernovae is almost identical to that observed in several novae. The present investigation is concerned with the question whether the thermal infrared radiation from SN 1979c and SN 1980k could have been emitted by dust particles which were present in a circumstellar shell prior to the supernova event. The obtained results confirm the suggestion of Bode and Evans (1980) that the thermal emission from SN 1979c may have originated from preexisting dust present in a circumstellar shell and heated up by the UV-visual output of the supernova. The thermal infrared emission from SN 1980k may have a similar origin.