GRAVITATIONAL MICROLENSING BY A GALACTIC BAR

Observations have found that the microlensing optical depth in the dir ection of the galactic center is larger than theoretical predictions. Here we investigate the effect a galactic bar has on microlensing. We use two models for the bar in order to find the range of microlensing predications. We find that sufficient optical depth in Baade's window can be attained with bars of significantly different geometries. The d ifference in geometry can be mapped out with the optical depths; howev er, this method may not be able to distinguish some bars from bulges. The time-scale distributions for different models are calculated and c ompared. Substantial disk microlensing may eventually be distinguishab le by an extended tail in the time-scale distribution. (C) 1995 Americ an Astronomical Society.