Spectrum of SN 1983n in NGC 5236 at maximum light

Abstract

The spectrum of SN 1983n in NGC 5236 (M83) obtained at its light maximum is presented. The spectrogram was digitized and smoothed using optimal filter technique in Fourier space. The moonlight background was subtracted after smoothing. Though the spectrum conforms to type I classification, it is peculier in that the characteristic 6150 A absorption is very weak and the helium lines are seen in emission. The peculiarity probably owes to the fact that the supernova was underluminous: The identifiable absorption features of HeI, OI, Fe II, S II, Si II and Ca II yield an expansion velocity of 12350 plus or minus 1910 km s/sup-1/, a value consistent with other type I supernovae