The Distances to Open Clusters from Main-Sequence Fitting. IV. Galactic Cepheids, the LMC, and the Local Distance Scale

We derive the basic properties of seven Galactic open clusters containing Cepheids and construct their period-luminosity (P-L) relations. For our cluster main-sequence fitting we extend previous Hyades-based empirical color-temperature corrections to hotter stars using the Pleiades as a template. We use -->BVICJHKs data to test the reddening law and include metallicity effects to perform a more comprehensive study for our clusters than prior efforts. The ratio of total to selective extinction -->RV that we derive is consistent with expectations. Assuming the LMC P-L slopes, we find --> MV = ? 3.93 ? 0.07 (statistical) ? 0.14 (systematic) for 10 day period Cepheids, which is generally fainter than those in previous studies. Our results are consistent with recent HST and Hipparcos parallax studies when using the Wesenheit magnitudes -->W(VI) . Uncertainties in reddening and metallicity are the major remaining sources of error in the V-band P-L relation, but a higher precision could be obtained with deeper optical and near-infrared cluster photometry. We derive distances to NGC 4258, the LMC, and M33 of -->(m ? M)0 = 29.28 ? 0.10, -->18.34 ? 0.06, and -->24.55 ? 0.28, respectively, with an additional systematic error of 0.16 mag in the P-L relations. The distance to NGC 4258 is in good agreement with the geometric distance derived from water masers [ -->? (m ? M)0 = 0.01 ? 0.24], our value for M33 is less consistent with the distance from an eclipsing binary [ -->? (m ? M)0 = 0.37 ? 0.34], and our LMC distance is moderately shorter than the adopted distance in the HST Key Project, which formally implies an increase in the Hubble constant of -->7% ? 8% .