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 Hubble Space Telescope .
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 \pm 0.26 mag , corresponding to a distance of 16.0 \pm 1.9 Mpc .
Our distance estimate is based on values of \mu _ { 0 } = 18.50 \pm 0.10 mag and E ( V–I ) = 0.13 mag for the distance modulus and reddening of the LMC , respectively .