The Optical Gravitational Lensing Experiment. Gaia South Ecliptic Pole Field as Seen by OGLE-IV

摘要

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 outskirtsof the LMC, based on the data collected during the fourth phase of the OpticalGravitational Lensing Experiment, OGLE-IV. The GSEP field will be observedduring the commissioning phase of the ESA Gaia space mission for testing andcalibrating the Gaia instruments. We provide the photometric maps of the GSEP region containing the mean VIphotometry of all detected stellar objects and their equatorial coordinates. Weshow the quality and completeness of the OGLE-IV photometry and color-magnitudediagrams of this region. We conducted an extensive search for variable stars in the GSEP field leadingto the discovery of 6789 variable stars. In this sample we found 132 classicalCepheids, 686 RR Lyr type stars, 2819 long-period, and 1377 eclipsingvariables. 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 conducteda search for optical transients. We discovered two firm type Ia supernovae andnine additional supernova candidates. To facilitate future Gaia supernovaedetections we prepared a list of more than 1900 galaxies to redshift about 0.1located in the GSEP field. Finally, we present the results of astrometric study of the GSEP field. Withthe 26 months time base of the presented here OGLE-IV data, proper motions ofstars could be detected with the accuracy reaching 2 mas/yr. Astrometry allowedto distinguish galactic foreground variable stars detected in the GSEP fieldfrom LMC objects and to discover about 50 high proper motion stars (propermotion >100 mas/yr). Among them three new nearby white dwarfs were found.