Type I supernova 1974g in NGC 4414

Photographic image-tube spectra (150 Å mm^–1, 4500 Å-7000 Å) of the type I supernova (1974g) in the Sc galaxy NGC 4414 obtained at phases+ 14 days and + 40 days past maximum light have been reduced to absolute flux. The positions of various spectral features and the overall appearance of the spectra of SN 1974g closely match previously observed type I SN spectra at similar phases. An electronographic isophotal map of NGC 4414 is presented, and an accurate position of SN 1974g given. A distance to NGC 4414 of 15 Mpc was determined from the recessional velocities and the diameters of Hii regions; while the absolute magnitude at maximum light of SN 1974g was found to beM _B(max)=–19.0. Estimates of the radius of the expanding photosphere of SN 1974g, cetermined by two independent methods, giveR10¹⁵ cm in the early post-maximum phases. The time of outburst,t=–25 days, has been estimated for SN 1974g. By assuming the broad emission feature observed at 6480 Å to be H, very rough estimates of the electron density and the mass of ionized hydrogen in the expanding supernova envelope are given. The total (observed) luminous energy of SN 1974g was 10⁵¹ erg.