Stellar contribution to the Galactic bulge microlensing optical depth

We estimate the optical depth to self-lensing by stars in the Galactic bulge using the Hubble Space Telescope star counts of Holtzman et al. and Zoccali et al. as extrapolated by Gould into the brown dwarf and remnant regimes and deprojected along the line of sight using the model of Dwek et al. We find a self-lensing optical depth tau (bulge - bulge) = 0.98 x 10(-6). When combined with the lensing of bulge stars by foreground stars in the disk, this yields tau (bulge - total) = 1.63 x 10(-6), in reasonable agreement with the estimates of tau = 2.13 +/- 0.40 x 10(-6) and tau = 1.08 +/- 0.30 x 10(-6) based on observations of clump giants by the MACHO and EROS collaborations.