Lens system configurations for the close (upper panel) and wide (lower panel) 2L1S models. In each panel, the curve with an arrow is the source trajectory and the cuspy close figures represent the caustics. The caustic shape varies depending on time due to the variation in the M₁ –M₂ separation induced by the lens orbital motion, and the presented caustic is the one corresponding to the time of the anomaly, that is, HJD′~ 8107.7. The gray curves around the caustic are the equi-magnification contours. The four empty circles on the source trajectory drawn in magenta color represent the source locations at t₁ = 8210.617, t₂ = 8210.719, t₃ = 8210.776, and t₄ = 8210.863. The size of the circle is arbitrarily set and not scaled to the source size. The inset in each panel shows a wider view including both central and planetary caustics.