OPTICAL-DETECTION OF THE REMNANT OF SN-1980K IN NGC-6946

Optical CCD images of the site of SN 1980K in NGC 6946 reveal faint Hα emission which remained constant to ±0.2 mag between 1987.5 and 1988.6. A low-dispersion spectrum (FWHM = 11 Å) taken in 1988 August shows both narrow and broad Ha line emission, broad [O I], [O III], [Fe II], and [Ca II] and/or [O II] emission, and a faint, underlying blue continuum at ≈24 mag. All broad emission lines appear to have mean blueshifted line centers, possibly indicating the formation of dust within SN 1980K's ejecta. Expansion velocities suggest two chemically distinct regions; i.e., a hydrogen-rich (Vexp ≈ 7000 km s-1) zone plus an oxygen- and iron-rich zone (Vexp ≈ 5300-5500 km s-1). The narrow Hα emission likely originates in the supernova's circumstellar material with the faint blue continuum arising from the presupernova's parent OB association. Detection of optical emission from SN 1980K nearly 8 years after 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.