AAS Meeting #193 - Austin, Texas, January 1999
Session 47. Supernovae
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[47.03] Direct Analysis of Spectra of the Type~Ia Supernova 1994D

K. Hatano, D. Branch, E. Baron (U. Oklahoma)

SN~1994D, in the Virgo cluster galaxy NGC 4526, is the best observed Type~Ia supernova. We use the parameterized supernova synthetic--spectrum code SYNOW to make a direct analysis of observed spectra of SN~1994D throughout its photospheric phase. The synthetic spectra match the observed spectra in considerable detail. We find evidence from the spectra that the temperature at the photosphere increased from about 11 to 4 days before maximum light, and then began to decrease, in accord with the behavior of the broad--band colors of SN~1994D, and we see evidence in the spectra for the expected conversion of radioactive nickel to cobalt and then iron. We establish constraints on the composition structure of the ejected matter (composition versus ejection velocity). For example, sulfur and magnesium were confined to rather narrow velocity intervals similar to those of the unmixed carbon deflagration model W7. Spectra obtained well before maximum light show evidence for carbon moving as slowly as 12,000 km s-1, in contrast to the minimum carbon velocity of 26,000 km s-1 that we found previously for the Type~Ia SN~1990N. These and our other constraints can be used to restrict the range of hydrodynamical models that could represent SN~1994D.


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