The Optical Gravitational Lensing Experiment. Gaia South Ecliptic Pole
  Field as Seen by OGLE-IV
  We present a comprehensive analysis of the Gaia South Ecliptic Pole (GSEP)
field, 5.3 square degrees area around the South Ecliptic Pole on the outskirts
of the LMC, based on the data collected during the fourth phase of the Optical
Gravitational Lensing Experiment, OGLE-IV. The GSEP field will be observed
during the commissioning phase of the ESA Gaia space mission for testing and
calibrating the Gaia instruments.
  We provide the photometric maps of the GSEP region containing the mean VI
photometry of all detected stellar objects and their equatorial coordinates. We
show the quality and completeness of the OGLE-IV photometry and color-magnitude
diagrams of this region.
  We conducted an extensive search for variable stars in the GSEP field leading
to the discovery of 6789 variable stars. In this sample we found 132 classical
Cepheids, 686 RR Lyr type stars, 2819 long-period, and 1377 eclipsing
variables. Several objects deserving special attention were also selected,
including a new classical Cepheid in a binary eclipsing system.
  To provide empirical data for the Gaia Science Alert system we also conducted
a search for optical transients. We discovered two firm type Ia supernovae and
nine additional supernova candidates. To facilitate future Gaia supernovae
detections we prepared a list of more than 1900 galaxies to redshift about 0.1
located in the GSEP field.
  Finally, we present the results of astrometric study of the GSEP field. With
the 26 months time base of the presented here OGLE-IV data, proper motions of
stars could be detected with the accuracy reaching 2 mas/yr. Astrometry allowed
to distinguish galactic foreground variable stars detected in the GSEP field
from LMC objects and to discover about 50 high proper motion stars (proper
motion >100 mas/yr). Among them three new nearby white dwarfs were found.
