Optical detection of the remnant of SN 1980K in NGC 6946

Abstract

This paper discusses imaging and spectroscopic data collected with the Cassegrain CCD detector on the 3-m Shane telescope at the Lick Observatory on SN 1980K in NGC 6946 between seven and eight years after maximum. The spectrum of SN 1980K taken in 1987 revealed the presence of faint unresolved H-alpha emission coincident with the supernova's reported position, which remained constant to + or - 0.2 mag between 1987.5 and 1988.6. Guided by the H-alpha interference filter images, a 3-hr-long low-dispersion spectrum was obtained in August 1988, showing several broad emission lines on top of the faint continuum. The detection of optical emission from SN 1980K nearly eight years after the outburst indicates the formation of a young bright supernova remnant and suggests that similarly detectable levels of optical emission may exist from other young historical extragalactic supernovae, particularly those with detectable radio emission. 42 refs.