Greyscale plot (lower-left panel) showing the phase folded spectra in the region around Hγ, after shifting to the rest frame of the primary and subtracting the mean spectrum (upper-right panel) computed from the least contaminated phases. After shifting to the rest frame of the secondary and summing all phases, the emission profile of the secondary emerges (upper-left panel). Summing each phase-binned spectrum in a window 20 Å wide, and centred on Hγ in the rest frame of the secondary, produces the phase profile shown in the lower-right panel.