K‐Corrections and Spectral Templates of Type Ia Supernovae

Abstract

With the advent of large dedicated Type Ia supernova (SN Ia) surveys, K-corrections of SNe Ia and their uncertainties have become especially important in the determination of cosmological parameters. While K-corrections are largely driven by SN Ia broadband colors, it is shown here that the diversity in spectral features of SNe Ia can also be important. For an individual observation, the statistical errors from the inhomogeneity in spectral features range from 0.01 (where the observed and rest-frame filters are aligned) to 0.04 (where the observed and rest-frame filters are misaligned). To minimize the systematic errors caused by an assumed SN Ia spectral energy distribution (SED), we outline a prescription for deriving a mean spectral template time series that incorporates a large and heterogeneous sample of observed spectra. We then remove the effects of broadband colors and measure the remaining uncertainties in the K-corrections associated with the diversity in spectral features. Finally, we present a template spectroscopic sequence near maximum light for further improvement on the K-correction estimate. A library of $600 observed spectra of $100 SNe Ia from heterogeneous sources is used for the analysis.

The slowly declining type Ia supernova 2008fv and the near-infrared second maximum

“…The expected magnitudes for each band of the two (our & standard) photometric systems are derived by assuming the same input spectral energy distribution (SED). In particular, we use i) SN spectral template provided by Hsiao et al (2007) and ii) several S,ED obtained from the Kurucz atmosphere stellar models having different temperatures and chemical compositions. As a result, we find that the A57, page 4 of 16 difference between the magnitude measured with a standard filter Johnson (1965), Bessell (1979Bessell ( , 1990, and the TNT V, R, I filters are smaller than the photometric uncertainties adopted in the present work for our photometric results.…”

“…The SN SED is needed to achieve this goal (Leibundgut 1990;Hamuy et al 1993;Nugent et al 2002;Hsiao et al 2007). Briefly, we recall that the K term correction at an effective wavelength λ i in the X band can be written as…”

“…In the absence of spectral observation of SN 2008fv, we assumed the spectral template provided by Hsiao et al (2007) and obtained as the combination of about 1000 observed spectra of ∼100 SNe. We adopted the specific response curves of our photometric system, both in optical and in the infrared.…”

Testing supernovae Ia distance measurement methods with SN 2011fe

“…The high apparent brightness allowed us to obtain accurate, high signal-to-noise photometry, while the very low redshift (z = 0. 000804, de Vaucouleurs et al 1991) of its host galaxy, M101 (NGC 5457), eliminates the necessity of K-corrections for the photometry that otherwise would be a major source of systematic errors plaguing the distance determination (Hsiao et al 2007;Hsiao 2009). The low interstellar reddening is also a very fortunate circumstance, because all complications regarding the handling of the effect of interstellar dust (galactic vs. non-standard reddening, disentangling A&A 546, A12 (2012) reddening and intrinsic color variation, etc.)…”

Photometric properties of intermediate-redshift Type Ia supernovae observed by the Sloan Digital Sky Survey-II Supernova Survey

“…We use the spectrum of Hsiao et al (2007) for the K-correction. Ideally, we should apply a spectrum template based on the proper type of each SN Ia (e.g.…”