Possible models for the type IA supernova 1990N

Possible interpretations of new spectral and photometric features of Type Ia supernova 1990N with carbon deflagration/detonation models are presented. To explain the presence of Si and Ca at high expansion velocities in SN 1990N, we suggest four possible models, among which is a carbon detonation in a white dwarf with a mass ~1 M_sun_. The slow rise of the light curve of SN 1990N can be reproduced by both the deflagration and detonation models if the optical opacity is somewhat larger than that previously adopted. Implications for the Hubble constant are discussed.