STELLAR VARIABILITY BACKGROUND IN OGLE-I MICROLENSING SEARCH

We search OGLE-I photometric database for stars which, as defined by f ormal criteria adopted by OGLE-I microlensing search, showed variabili ty during only one out of 3 or 4 observing seasons. The results includ e 17 previously reported microlensing events, 2 newly discovered candi date events and 15 intrinsically variable stars that have a potential of contaminating samples of microlensing events. Based on photometry o btained in 1992 and 1993 OGLE #10 was tentatively included in the list of microlensing candidates, however its light curve in 1994 and 1995 shows many characteristics of the variable stars found in our search, and most likely it is not a microlensing event. For all stars which pa ssed our tests, we provide 44 x 44 arcsec (101 x 101 pixel) centered s ubframes from each OGLE-I frame in the I-band. It is the first time wh en images used to derive photometry of microlensing events are availab le in convenient format to astronomical community.