Top panel: occultation data (dots) for α Cnc, and best fit by a point-like source (solid line). The fit residuals are shown in the lower panel, enlarged for clarity. The curves labeled (a) and (b) are models for a binary star with equal components and projected separations of 3 and 10 mas, respectively. They are shown, shifted by arbitrary vertical offsets for clarity, to prove the inconsistency of the data with such scenarios.