Type Ia supernovae are a remarkably good standard candle and are bright enough to solve the Hubble Constant debate if only one or a a few could be calibrated in peak absolute magnitude. Recently, the Hubble Space Telescope has measured Cepheid distances to the host galaxies of five Type Ia events. But for these measures to be useful, the peak apparent magnitudes must be known. In many of the five cases, there are significant problems involving poor comparison stars, use of only a small subset of the available data, poor measures of photographic plates, and improper color terms. I have measured the comparison stars on modern magnitude systems, remeasured old plates, located overlooked and unpublished data, applied correct color terms, and fitted light curve templates in a quantitative manner. The result is the best possible peak magnitudes for SN1895B, SN1937C, SN1960F, SN1972E, and SN1981B variously in the U, B, V, and H bands. These peak magnitudes can then be combined with the HST distances and the calibration of the Calan-Tololo team to yield many independent measures of the Hubble Constant. All measures range from 50 to 63, with a weighted mean of 56+-2 km/s/Mpc.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1995