DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. VI. Variables in the Central Part of M33

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Abstract
The DIRECT project aims to determine direct distances to two important galaxies in the cosmological distance ladder—M31 and M33—using detached eclipsing binaries (DEBs) and Cepheids. We present the results of the first large-scale CCD-based search for variables in M33. We have observed two fields located in the central region of M33 for a total of 95 nights on the F. L. Whipple Observatory 1.2 m telescope and 36 nights on the Michigan-Dartmouth-MIT 1.3 m telescope. We have found a total of 544 variables, including 251 Cepheids and 47 eclipsing binaries. The catalog of variables is available on-line, along with finding charts and BVI light curve data (consisting of 8.2 × 104 individual measurements). The complete set of CCD frames is available upon request.