THE NEAR MAXIMUM-LIGHT SPECTRUM OF THE TYPE-IC SUPERNOVA 1987M

An analysis of the near-maximum-light optical and near-UV spectrum of the Type Ic supernova 1987M is presented. In the spectrum, in addition to the fairly certain identifications of O I, Ca II, and optical Fe II lines, we identify a weak H-alpha line, a moderately weak Si II lambda-6355 doublet, and the He I lambda-5876 line. The near-UV region of the spectrum is found to result from a blend of iron peak ion lines, with only solar abundances of the iron peak elements required in the supernova atmosphere. It is concluded that hydrogen is underabundant relative to solar composition in the supernova atmosphere by at least a factor of 10; no lower limit on hydrogen abundance has been determined. It is also concluded that a helium star model for Type Ic supernovae is adequate and slightly favored for explaining the analyzed spectrum. The implications of the spectrum analysis for explosion models of Types Ib and Ic supernovae are discussed.