Type Ia SN 2012ij opt. & NIR spectra

The B-band light curve exhibits a fast postpeak decline with {Delta}m_15_(B)=1.86+/-0.05mag. All the R- and I/i-band light curves show a weak secondary peak/shoulder feature at about 3 weeks after the peak, like some transitional subclass of SNe Ia, which could result from an incomplete merger of near-infrared (NIR) double peaks.

The spectra are characterized by TiII and strong SiII{lambda}5972 absorption features that are usually seen in low-luminosity objects like SN 1999by. The NIR spectrum before maximum light reveals weak carbon absorption features, implying the existence of unburned materials. We compare the observed properties of SN 2012ij with those predicted by the sub- Chandrasekhar-mass and the Chandrasekhar-mass delayed-detonation models and find that both optical and NIR spectral properties can be explained to some extent by these two models.