Spectral Analysis of SN 1993J
Session 39 -- SN1993J, SN1978K and SN1987A
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [39.02] Spectral Analysis of SN 1993J

E. Baron$^\dagger$, P. H. Hauschildt$^*$, and D. Branch$^\dagger$ ($\dagger$Dept of Physics and Astronomy, Univ. of Oklahoma, Norman, OK 73019; $^*$Dept. of Physics and Astronomy, Arizona State Univ., Tempe, AZ 85287)

We present results of model calculations of synthetic spectra for a time series of observations of the Type IIpec supernova SN 1993 in M81. We find that at very early times the composition was likely to be roughly solar and the atmosphere was rather extended. The structure quickly evolved to be extremely steep with equivalent power-law indices at the photosphere'' of $N \approx 20-40$ and the composition became significantly enhanced in helium with $Y \approx 0.8$. We find the helium is excited by non-thermal ionization from fast electrons produced by the Comptonization of gamma rays from the decay of $\sim 0.1 {\rm M}_\odot$ of $^{56}$Ni. We find a distance to the supernova consistent with that of the recently determined Cepheid distance. We compare our distance with other published distance determinations. We also discuss discrepancies between our models and the observations.