Simulation of the microlensing effect produced by a binary star. Left panel: source plane micro-caustics (black) created by a pair of stars located at the position of image B in the lens plane. The green and orange triangles show the stars’ locations, which are separated by 200 AU. The inset panel zooms in onto the position of the accretion disk. The light (dark) blue circle corresponds to the accretion disk size R₀ (size of the ISCO, R_ISCO). Right panel: magnitude change of image B due to the periodic motion of the microlenses. An animated version of this figure is available online.