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E.J. Lentz, E. Baron, D. Branch (U. Oklahoma), P.H. Hauschildt (U. Georgia)
Supernova SN~1984A shows unusually large expansion velocities in lines from freshly synthesized material, relative to typical Type~Ia supernovae (SNe~Ia). SN~1984A represents an extreme example of SNe~Ia with large expansion velocities, but otherwise normal spectra. We have modeled several early spectra of SN~1984A with the multi-purpose NLTE model atmosphere and spectrum synthesis code, {\tt PHOENIX}. We have used as input two delayed detonation models, DD21c (Höflich et al. 1998) and CS15DD3 (Iwamoto et al. 1999). These models show line expansion velocities which are larger than for typical deflagration models like W7 (Nomoto et al. 1984, Thielemann et al. 1986), which we have previously shown to fit normal SNe~Ia quite well (Lentz et al. 2000). Higher densities of newly synthesized material from burning at higher velocities are found in delayed detonation models than in deflagration models. We find these delayed detonation models to be reasonable approximations to high expansion velocity SNe~Ia like SN~1984A. Even if the explosion mechanism of the delayed detonation models is incorrect, the density of synthesized material at high velocities is of the right magnitude.