DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. I. Variables in the Field M31B

Abstract

We undertook a long term project, DIRECT, to obtain the direct distances to\ntwo important galaxies in the cosmological distance ladder -- M31 and M33,\nusing detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult\nto detect, detached eclipsing binaries provide us with the potential to\ndetermine these distances with an accuracy better than 5%. The massive\nphotometry obtained in order to detect DEBs provides us with good light curves\nfor the Cepheid variables. These are essential to the parallel project to\nderive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both\nCepheids and eclipsing binaries the distance estimates will be free of any\nintermediate steps.\n As a first step of the DIRECT project, between September 1996 and January\n1997 we have obtained 36 full nights on the Michigan-Dartmouth-MIT (MDM)\n1.3-meter telescope and 45 full/partial nights on the F. L. Whipple Observatory\n(FLWO) 1.2-meter telescope to search for detached eclipsing binaries and new\nCepheids in the M31 and the M33 galaxies. In this paper, first in the series,\nwe present the catalog of variable stars, most of them newly detected, found in\nthe field M31B ($\\alpha_{2000.0},\\delta_{2000}=11.20\\deg,41.59\\deg$). We have\nfound 85 variable stars: 12 eclipsing binaries, 38 Cepheids and 35 other\nperiodic, possible long period or non-periodic variables. The catalog of\nvariables, as well as their photometry and finding charts, are available using\nthe anonymous ftp service and the WWW.\n