GRAVITATIONAL MICROLENSING OF THE GALACTIC BULGE STARS

We estimate the optical depth to gravitational microlensing due to kno wn stellar populations to be approximately 8.5 x 10(-7) for the Galact ic bulge stars in the Baade Window. The contribution of the bulge and disk stars to the optical depth is approximately 60% and approximately 40%, respectively, all numbers being uncertain. If the stellar mass f unction is approximated as N(M) approximately M-2 for 0.1 less-than-or -equal-to M/M. less-than-or-equal-to 1.0 then the expected frequency o f events with amplitude larger than A = 1.34 is GAMMA(bulge) almost-eq ual-to 10 and GAMMA(disk) almost-equal-to 2 events per year per 10(6) stars. If the bulge is elongated along the line of sight then the rate GAMMA(bulge) may be still higher. The overall distribution of event t imescales is expected to peak at t0 = r(E)/v almost-equal-to 10 days.