Exploring the Variable Sky with LINEAR. I. Photometric Recalibration
  with SDSS
  We describe photometric recalibration of data obtained by the asteroid survey
LINEAR. Although LINEAR was designed for astrometric discovery of moving
objects, the dataset described here contains over 5 billion photometric
measurements for about 25 million objects, mostly stars. We use SDSS data from
the overlapping ~10,000 deg^2 of sky to recalibrate LINEAR photometry, and
achieve errors of 0.03 mag for sources not limited by photon statistics, with
errors of 0.2 mag at r~18. With its 200 observations per object on average,
LINEAR data provide time domain information for the brightest 4 magnitudes of
SDSS survey. At the same time, LINEAR extends the deepest similar wide-area
variability survey, the Northern Sky Variability Survey, by 3 mag. We briefly
discuss the properties of about 7,000 visually confirmed periodic variables,
dominated by roughly equal fractions of RR Lyrae stars and eclipsing binary
stars, and analyze their distribution in optical and infra-red color-color
diagrams. The LINEAR dataset is publicly available from the SkyDOT website
(http://skydot.lanl.gov).
