The peak brightness of sn 1895b in NGC 5253 and the hubble constant

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The light curve of the Type Ia supernova SN 1895B (in NGC 5253) is important because Sandage et al. have measured a distance to the host galaxy by means of Cepheid variables and thus have derived the Hubble constant. However, the last time the supernova plates were measured was in 1923, and the resultant photometry is inconsistent at the 0.8 mag level. In this paper, I report on the results of my remeasurement of the old supernova plates with a scanning microdensitometer. I find R-magnitudes of > 11.3 ± 0.3, 8.36 ± 0.07, 8.51 ± 0.06, 8.54 ± 0.05, and 9.34 ± 0.08 on JD 2,413,359,2,413,383, 2,413,384, 2,413,385, and 2,413,393, respectively. The last plate was a prism plate, for which I present a flux-calibrated spectrum, taken - 15 days after maximum. Even though only loose constraints can be placed on the light curve shape, the firm limit on the peak magnitude (<8.49 ± 0.03) will provide a firm limit on the Hubble constant. The most likely shape is that of the average Type Ia template of Leibundgut et al., for which the best-fit peak R-magnitude is 8.26 ± 0.11. The deduced probability distribution for H0 is peaked at 51 ± 7 km s-1 Mpc-1, with extreme limits of 61 ± 12 and 26 ± 5 km s-1 Mpc-1. © 1995 The American Astronomical Society.

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Astrophysical Journal

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