The Peak Brightness of SN 1974G in NGC 4414 and the Hubble Constant

The light curve of the Type Ia supernova SN1974G (in NGC4414) is importantbecause the Hubble Space Telescope has measured the distance to the host galaxyby means of Cepheid variables and thus the Hubble Constant can be derived.Light curves from the secondary literature are inadequate since the majority ofdata is misreported, the majority of the published data is overlooked, and themajority of all data is unpublished, while comparison star sequences haveoffsets of over half a magnitude. I have recovered and validated all data,remeasured the comparison stars, and performed light curve template fits. Ifind the observed peak B and V magnitudes to be $12.48 \pm 0.05$ and $12.30 \pm0.05$, with a decline rate of $\Delta m_{15} = 1.11 \pm 0.06$. For $E(B-V) =0.16 \pm 0.07$, the unabsorbed peak magnitudes are $B = 11.82 \pm 0.29$ and $V= 11.80 \pm 0.22$. With the distance modulus to NGC4414 as $\mu = 31.41 \pm0.23$, I find $H_{0} = 55 \pm 8 km \cdot s^{-1} \cdot Mpc^{-1}$.Comment: 18 pages, 2 figures, Accepted for publication in Ap