We compute the predicted optical depth and duration distribution of microlensing events towards Baade ’ s window in a model composed of a Galactic disk and a bar .
The bar model is a self-consistent dynamical model built out of individual orbits that has been populated to be consistent with the COBE maps of the Galaxy and kinematic observations of the Bulge .
We find that most of the lenses are in the Bulge with a line-of-sight distance 6.25 kpc ( adopting R _ { 0 } = 8 kpc ) .
The microlensing optical depth of a 2 \times 10 ^ { 10 } M _ { \odot } bar plus a truncated disk is ( 2.2 \pm 0.3 ) \times 10 ^ { -6 } , consistent with the very large optical depth ( 3.2 \pm 1.2 ) \times 10 ^ { -6 } found by Udalski et al .
( 1994 ) .
This model optical depth is enhanced over the predictions of axisymmetric models by Kiraga & Paczyński ( 1994 , hereafter KP ) by slightly more than a factor of two since the bar is elongated along the line-of-sight .
The large Einstein radius and small transverse velocity dispersion also predict a longer event duration in the self-consistent bar model than the KP model .
The event rate and duration distribution also depend on the lower mass cutoff of the lens mass function .
With a 0.1 M _ { \odot } cutoff , 5-7 events ( depending on the contribution of disk lenses ) with a logarithmic mean duration of 20 days are expected for the OGLE experiment according to our model , while Udalski et al .
( 1994 ) observed 9 events with durations from 8 to 62 days .
On the other hand , if most of the lenses are brown dwarfs , our model predicts too many short duration events .
A KS test finds only 7 % probability for the model with 0.01 M _ { \odot } cutoff to be consistent with current data .