Left panel: VLT-FLAMES OB1 (blue) and OB2 (magenta) Hα profiles resulting from subtraction of the underlying spectrum of the narrow-lined B-type star. Horizontal lines, same color coding, represent the rest frame velocity of the primary at these epochs. Note that a small residual velocity shift is still apparent (cf Fig. 1). Right panel: the same profiles plotted in their rest frame velocities; OB1 and OB2 spectra in blue and magenta respectively, the merged spectrum is plotted in black. Also illustrated are the velocities of the double peaks (±155 km s⁻¹), the full-width half-maximim (FWHM) of the emission (550 km s⁻¹), and the extent to which emission is present in the line wings (±500 km s⁻¹). These spectra were taken ∼34 days apart and some variability is apparent within the double-peaked structure of the profile.