The unique supernova (1985f) in NGC 4618

The complete optical spectrum (3200-10,000 A) of supernova 1985f in NGC 4618 is presented. Strong emission lines of O, Ca, C, Mg, Na, Fe and N are present, while H and He absorption lines are conspicuously absent. The spectrum of SN 1985f does not resemble any previously published spectra of supernovae, and it is postulated that its progenitor was a massive Wolf-Rayet star that expelled its outer atmosphere of H and He prior to supernova explosion. Photographs of SN 1985f are provided which illustrate its location in very bright H II regions near the nucleus of NGC 4618. The supernova, so faint at the time of discovery, is overwhelmed by light from the surrounding galaxy in any moderately deep image. A plate obtained in May 1914 reveals the absence of a starlike object at the expected position, and visual observations made in November 1985 indicate that the supernova has faded substantially since March 1985.