THE PEAK BRIGHTNESS OF SN-1937C IN IC-4182 AND THE HUBBLE CONSTANT

The light curve of the Type Ia supernova SN 1937C (in IC 4182) is impo rtant because Sandage et al. have measured a distance to the host gala xy by means of Cepheid variables and thus have derived the Hubble cons tant. However, the peak brightness of SN 1937C has only been derived w ith the relatively poor original comparison star brightnesses and with out regard to a large body of data in the literature. In this paper, I will correct these and other procedural difficulties. I find that the late time photographic light curve appears to have a broken exponenti al decay with equivalent half-lives of 46 and 58 days with the break n ear 300 days after maximum. I also find that the peak B-magnitude was 8.71 +/- 0.14 on JD 2428770.0 +/- 1.0 at which time the B - V was -0.0 3 +/- 0.13. With these improved peak brightnesses, the distance modulu s of Sandage et al., and peak absolute magnitudes in the center of the range of modem estimates, I derive the Hubble constant to be 50 km s- 1 Mpc-1.