About 3% of microlensing events caused by lenses in the Galactic bulge (bar) should show a noticeable effect due to the stellar size of the lensed star (source). We suggest focusing the observations (in a separate project) mainly on red clump stars and red giants because the chance to observe a transit event is proportional to the radius of the lensed star and therefore several times higher for these cases. In addition, we discuss the influence of the average lensing mass and the depth (extension) of the Galactic bulge on the probability to detect a transit event. Small color effects due to the different limb darkening of the star at different wavelengths might be measurable for events where the impact parameter is smaller than the radius of the lensed star and when the peak magnitude is brighter than 15.5 mag in the I band in the Baade window.
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H. J. Witt (1995) studied this question.
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