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The light curve of the Type Ia supernova SN 1974G (in NGC 4414) is important because the Hubble Space Telescope has measured the distance to the host galaxy by means of Cepheid variables, and thus the Hubble constant can be derived. Light curves from the secondary literature are inadequate, since the majority of data is misreported, the majority of the published data is overlooked, and the majority of all data is unpublished, while comparison-star sequences have offsets of over half a magnitude. I have recovered and validated all data, remeasured the comparison stars, and performed light-curve template fits. I find the observed peak B and V magnitudes to be 12.48 ± 0.05 and 12.30 ±0.05, with a decline rate of Δm15 = 1.11 ± 0.06. For E(B-V) = 0.16 ± 0.07, the unabsorbed peak magnitudes are B = 11.82 ± 0.29 and V = 11.80 ± 0.22. With the distance modulus to NGC 4414 as μ = 31.41 ± 0.23, I find H0 = 55 ±8 km s-1 Mpc-1. © 1998. The American Astronomical Society. All rights reserved.

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Astrophysical Journal

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