Using SN Ia Light Curve Shapes to Measure The Hubble Constant

We present an empirical method which uses visual band light curve shapes (LCS) to estimate the luminosity of type Ia supernovae (SN Ia). This method is first applied to a ``training set'' of 8 SN Ia light curves with independent distance estimates to derive the correlation between the LCS and the luminosity. We employ a linear estimation algorithm of the type developed by Rybicki and Press (1992). The result is similar to that obtained by Hamuy et al. (1995a) with the advantage that LCS produces quantitative error estimates for the distance. We then examine the light curves for 13 SN Ia to determine the LCS distances of these supernovae. The Hubble diagram constructed using these LCS distances has a remarkably small dispersion of $\sigma_V$ = 0.21 mag. We use the light curve of SN 1972E and the Cepheid distance to NGC 5253 to derive $67 \pm 7$ km s$^{-1}$ Mpc$^{-1}$ for the Hubble constant.