Sub-Chandrasekhar progenitors for Type Ia SNe

From the ratio of the NIR lines to the optical lines limits can be placed on the temperature and density of the emission region. We find a similar evolution of these parameters across our sample.

Using the evolution of the FeII 12570-7155{AA} line as a prior in fits of spectra covering only the optical wavelengths we show that the 7200{AA} feature is fully explained by [FeII] and [NiII] alone. This approach allows us to determine the abundance of NiII/FeII for a large sample of 130 optical spectra of 58 SNe Ia with uncertainties small enough to distinguish between Chandrasekhar mass (M_Ch_) and sub-Chandrasekhar mass (sub-M_Ch_) explosion models.