Carnegie Supernova Project. II. NIR sp. of SNIa

These spectra, obtained with the FIRE spectrograph on the 6.5m Magellan Baade telescope, have a spectral range of 0.8-2.5{mu}m. Using this sample, we explore the NIR spectral diversity of SNe Ia and construct a template of spectral time series as a function of the light-curve-shape parameter, color stretch sBV.

Principal component analysis is applied to characterize the diversity of the spectral features and reduce data dimensionality to a smaller subspace. Gaussian process regression is then used to model the subspace dependence on phase and light-curve shape and the associated uncertainty. Our template is able to predict spectral variations that are correlated with sBV, such as the hallmark NIR features: MgII at early times and the H-band break after peak.