K. Kuijken, THE MAXIMUM OPTICAL DEPTH TOWARD BULGE STARS FROM AXISYMMETRICAL MODELS OF THE MILKY-WAY, The Astrophysical journal, 486(1), 1997, pp. 19-22
It has been known that recent microlensing results toward the bulge im
ply mass densities that are surprisingly high, given dynamical constra
ints on the Milky Way mass distribution. We derive the maximum optical
depth toward the bulge that may be generated by axisymmetric structur
es in the Milky Way, and we show that observations are close to surpas
sing these limits. This result argues in favor of a bar as a source of
significantly enhanced microlensing. Several of the bar models in the
literature are discussed.