Continued Monitoring of the Late-Time Optical Emission from SN 1980K

Abstract

A September 1994 spectrum of SN 1980K covering 5500-10000A shows broad Hα emission at a flux level of 1.4+/-0.2 x 10^15^ erg cm^-2^ s^-1^. When combined with previous measurements, these data set a 0.25 mag limit to the decrease of the supernova's Hα emission during the period 1987 to 1994. The Hα line profile appears narrower (FWHM= 190 A) than that seen in 1992, confirming a trend predicted by SN-circumstellar interaction models. However, neither a power law SN density profile nor one steeper like that expected in a red supergiant match all the observed relative line intensities. This new spectrum sets stringent limits on the presence of [C I] λ8729, the Ca II infrared triplet, and [S III] λ{lamba}9069,9531 emission at <= 0.25 x F(Hα, below that predicted by the favored power law SN envelope model.