The luminosities of supernovae of type Ia derived from Cepheid observations

Available data on the luminosities of supernovae of Type Ia (SNe Ia) that have been calibrated by Cepheids are collected and discussed. The objects in the present sample show a range of ~20 in luminosity. The data strongly confirm the suspicion that SNe Ia in early-type systems are, on average, fainter than those that occur in late-type galaxies. Historical observations of S Andromedae suggest that the maximum magnitude versus rate-of-decline relationship for SNe Ia exhibits a large intrinsic dispersion. This is not surprising because the amount of 56Ni that is produced, and other observable properties of SNe Ia, are expected to depend sensitively on how much fuel is ignited.