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A. Z. Bonanos, K. Z. Stanek, D, D. Sasselov (Harvard-Smithsonian, CfA), J. Kaluzny (N. Copernicus Astronomical Center, Poland), B. J. Mochejska (Harvard-Smithsonian, CfA), L. Macri (Univ. of Arizona)
The DIRECT project obtained about 170 nights on the FLWO 1.2-meter telescope and 35 nights on the MDM 1.3-meter telescope between 1996 and 1999 to search for detached eclipsing binaries and Cepheids in the M31 and the M33 galaxies. This was the first step in an ongoing program to improve the direct distance estimate to these two important galaxies in the cosmological distance ladder.
Detached eclipsing binaries provide us with the potential to determine these distances with an accuracy better than 5%. The massive photometry provides us with good lightcurves for known and new Cepheid variables. These are essential to the parallel project of deriving direct Baade-Wesselink distances to M31. With both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps.
We present the variables found in the 22'x22' field M31Y: 38 eclipsing binaries, 165 Cepheids, 17 other periodic variables and 46 miscellaneous variables. The observations were made in 1999 during 25 nights.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.