Diagnostic diagrams. Colour code is the same as in Fig. 1. Left panel: Hα FWHM versus its EW measured in a 44 Å-wide (∼2000 km s⁻¹) region centred at the rest frame of the binary. The quiescent values of EW and FWHM (Shahbaz et al. 1997; Garcia et al. 1999) are indicated as vertical and horizontal black dashed lines, respectively (grey bands indicate uncertainties). The FWHM quiescent value reported in Garcia et al. (1999) (830 ± 25 km s⁻¹) has been downgraded to the spectral resolution of our data. Right panel: Hα blue and red wing residuals (excesses) for the 14 epochs. The grey-shaded region indicates the 3σ significance contour.