The Optical Gravitational Lensing Experiment (OGLE)
Session 3 -- Instrumentation and Techniques I: Ground Based
Display presentation, Monday, June 12, 1995, 9:20am - 6:30pm

## [3.04] The Optical Gravitational Lensing Experiment (OGLE)

K. Z. Stanek, B. Paczy\'nski (Princeton University), A. Udalski, M. Szyma\'nski, J. Ka\l u\.zny, M. Kubiak (Warsaw University), M. Mateo (University of Michigan), W. Krzemi\'nski, G. W. Preston (Carnegie Observatories)

We continue observing microlensing events towards the Galactic bulge. The analysis of the first three years of the OGLE data revealed 12 microlensing events of the Galactic bulge stars, including first ever observed case of the microlensing by a binary star and first ever microlensing event discovered and observed in real time. A complete sample of nine events observed in 1992 and 1993 gave the optical depth to gravitational microlensing larger than $(3.3 \pm 1.2) \times 10^{-6}$, higher than expected.

There is a number of side projects utilizing the data collected for the microlensing search. The OGLE color magnitude diagrams reveal the presence of the Galactic bar and a low density inner disk region $\sim 4$ kpc in radius. First two parts of the catalogue of a few thousand variable stars were published and are available over the computer network.

When the Galactic bulge could not be observed we had a number of secondary targets. In 1993 one field in Sculptor dwarf galaxy was monitored and over 200 RR Lyrae stars were detected. Also, two globular clusters, 47 Tuc and Omega Cen, were monitored in 1993 and 1994 in a search for detached eclipsing binaries. So far three such systems were found in Omega Cen. In 1994 one field in the recently discovered Sagittarius dwarf galaxy was observed. We detected seven RR Lyrae variables belonging to the dwarf.

The dedicated, 1.3-m OGLE telescope is under construction on the Las Campanas site. The first light is expected by the Fall 1995.

The up-to-date information on the OGLE project, including catalogs of the variable stars is accessible over the Internet network from {\tt sirius.astrouw.edu.pl} host ({\tt 148.81.8.1}), using the anonymous ftp'' service (directory {\tt ogle}). The OGLE results are also available over the {\tt WWW} at : {\tt http://www.astrouw.edu.pl/\~\/udalski/ogle.html}.