MICROLENSING BY STARS

If faint dwarfs are responsible for the microlensing events observed i n the Galactic bulge, then light from the lensing star contributes to the observed brightness. The background and lensing stars generally ha ve different colors, and the relative brightness changes during the mi crolensing event. Therefore, microlensing light curves are not perfect ly achromatic if hydrogen-burning stars are the lenses. In most cases, the color shift will be too small to be observable, but we argue that given the current microlensing rates, it is plausible that a few colo r-shifted microlensing events could be observed in the near future, es pecially if strategies are optimized to search for them. Although rare , such events would be very interesting: Light curves in two (or more) bands could provide information about the masses of and distances to both stars as well as the transverse speed of the lensing star.