<i>K</i>‐Corrections and Spectral Templates of Type Ia Supernovae

Abstract

With the advent of large dedicated Type Ia supernova (SN Ia) surveys,\nK-corrections of SNe Ia and their uncertainties have become especially\nimportant in the determination of cosmological parameters. While K-corrections\nare largely driven by SN Ia broad-band colors, it is shown here that the\ndiversity in spectral features of SNe Ia can also be important. For an\nindividual observation, the statistical errors from the inhomogeneity in\nspectral features range from 0.01 (where the observed and rest-frame filters\nare aligned) to 0.04 (where the observed and rest-frame filters are\nmisaligned). To minimize the systematic errors caused by an assumed SN Ia\nspectral energy distribution (SED), we outline a prescription for deriving a\nmean spectral template time series which incorporates a large and heterogeneous\nsample of observed spectra. We then remove the effects of broad-band colors and\nmeasure the remaining uncertainties in the K-corrections associated with the\ndiversity in spectral features. Finally, we present a template spectroscopic\nsequence near maximum light for further improvement on the K-correction\nestimate. A library of ~600 observed spectra of ~100 SNe Ia from heterogeneous\nsources is used for the analysis.\n