A Generalized K Correction for Type IA Supernovae: Comparing R-band Photometry beyond z=0.2 with B, V, and R-band Nearby Photometry

Abstract

ABSTRACT. Photometric measurements show that, as a group, nearby Type la supernovae follow similar light curves and reach similar peak magnitudes (Branch and Tammann, ARAA, 30, 359, 1992). Thus, these supemovae may serve as standard candles or calibrated candles at cosmological distances. Magnitudes of local and distant supemovae, both in the same filter band, are compared using a Κ correction to account for the different spectral regions incident on that filter. A generalized approach compares magnitudes in different bands for the nearby and distant supemovae, bands that are selected to give sensitivity in corresponding regions of the unredshifted and redshifted spectra. Thus, R magnitudes for supemovae at z~0.5 are compared with Β magnitudes of local supemovae. We compute these generalized Κ corrections over a range of redshifts and bandpass pairs and discuss their advantages over the traditional single-band Κ correction. In particular, errors near maximum light can be kept below 0.05 mag out to at least ζ ^0.6, whereas the traditional Κ correction is less accurate and can be difficult to determine beyond ζ >0.2