Top: comparison between the normalized spectra computed without radiation pressure (in black) and with radiation pressure (in grey) for model 1. To better distinguish spectra, the black line is wider than the grey line. Orbital phases are, from bottom to top: phases 0.1, 0.25 and 0.4. The spectra are shifted vertically by 0.25 continuum units for clarity. Middle: corresponding residuals (spectrum with radiation pressure minus spectrum without radiation pressure). The residual plots are shifted by 0.015 for clarity. Bottom: logarithm of the ratio of the fluxed spectra with radiation pressure divided by the one without. These plot are shifted by 0.006 for clarity.