The Extragalactic Distance Scale Key Project. XVIII. The discovery of Cepheids and a new distance to NGC 4535 using the Hubble Space Telescope
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We report on the discovery of Cepheids in the Virgo spiral galaxy NGC 4535, based on observations made with the Wide Field and Planetary Camera 2 on board the Bubble Space Telescope (HST). NGC 4535 is one of 18 galaxies observed as a part of The HST Key Project on the Extragalactic Distance Scale, which aims to measure the Hubble constant to 10% accuracy. NGC 4535 was observed over 13 epochs using the F555W filter, and over 9 epochs using the F814W filter. The HST F555W and F814W data were transformed to the Johnson V and Kron-Cousins I magnitude systems, respectively. Photometry was performed using two independent programs, DoPHOT and DAOPHOT II/ALLFRAME. Period-luminosity relations in the V and I bands were constructed using 39 high-quality Cepheids present in our set of 50 variable candidates. We obtain a distance modulus of 31.02 + 0.26 mag, corresponding to a distance of 16.0 + 1.9 Mpc. Our distance estimate is based on values of 0 = 18.50 0.10 mag and E(V-I) = 0.13 mag for the distance modulus and reddening of the LMC, respectively.