Simulation of the photometric Rossiter-McLaughlin (R-M) effect for a pair of white dwarf stars rotating close to their break-up velocity in an eclipsing binary with a period of 39.1 min. Upper panels: light curve of the binary; the two lower panels: contribution to this light curve due to the photometric R-M effect. In all panels, the solid line is calculated using Roche geometry for stars with rotation axes aligned with the orbital axis and dashed lines are for models of spherical stars with λ = 60°.