Determination of the Hubble Constant Using a Two-Parameter Luminosity Correction for Type Ia Supernovae

In this paper, we make a comprehensive determination of the Hubble constant H0 by using two parameters—the B-V color and the rate of decline Δm15—to simultaneously standardize the luminosities of all nearby Cepheid-calibrated Type Ia supernovae (SNe Ia) and those of a larger, more distant sample of 29 SNe Ia. Each group is treated in as similar a manner as possible in order to avoid systematic effects. A simultaneous χ2 minimization yields a standardized absolute luminosity of the Cepheid-calibrated supernovae as well as the Hubble constant obtained from the more distant sample. With an adopted LMC distance modulus of 18.50, we find H0 = 62 km s-1 Mpc-1 and a standardized absolute magnitude of -19.46. The sensitivity of H0 to a metallicity dependence of the Cepheid-determined distances is investigated. The total uncertainty δH0, dominated by uncertainties in the primary distance indicators, is estimated to be 5 km s-1 Mpc-1.