(Top) Lens-plane geometry view of a binary lens of unequal masses (normalized so that M<sub>1</sub> + M<sub>2</sub> equals 1). The straight line indicates the source's relative motion during the event. The curved loop around both masses is the critical curve in the source plane; the spiky central region between the masses represents the caustic. (Bottom) The event lightcurve resulting from this configuration.
