Astrometric Shifts in the OGLE-1 Microlensing Events

Abstract

We measure the astrometric shifts of the light centroids for the microlensing events in the OGLE-1 database. Of the 15 consistently detected events, 7 had significant shifts which we were able to measure with a fair degree of confidence. Those events with large shifts are also expected to be unresolved with a background ``blend'', and thus, we suggest that we have identified events in the OGLE-1 catalog which are strongly blended. Though we concentrate on the OGLE-1 database, and use the DoPHOT package in order to perform our analysis, we suggest that this shift is a generic effect, and should be observable in any crowded field.