  The COROT space mission will monitor several target fields for up to 150 days
to perform asteroseismology and to search for extrasolar planets by photometric
transits. Variable stars in the target fields are important objects for
additional scientific studies but can also disturb the search for planetary
transits. A variability characterization of the target fields prior to COROT
observations is therefore important for two reasons: to find interesting
variable stars to monitor further and to make an analysis of the impact of the
variable stars on detecting extrasolar planet transits with COROT. The Berlin
Exoplanet Search Telescope (BEST) is a small wide-angle telescope dedicated to
high-precision photometry. It has observed a 9 square degree field of view
centered at (alpha, delta)=(19h00m00.0s, +00deg01'55.2") (J2000.0) over 98
nights to search for variable stars in the surroundings of the first long-run
target field (LRc1) of the COROT space mission. In this data set we identified
92 periodic variable stars, 86 of which are new discoveries and 6 of which are
known from the General Catalogue of Variable Stars (GCVS). For five of the GCVS
stars, variability could not be confirmed. Forty-three of the 92 detected
periodic variable stars are identified as eclipsing binaries. We have evaluated
the completeness of our survey for eclipsing binaries by comparing it to the
expected fraction of eclipsing binaries based on Hipparcos observations. From
this evaluation we show that the BEST data set presented here has a
completeness of 20%-30% for periods longer than 1 day and is complete relative
to Hipparcos for short-period binaries.
