Hα diagnostic diagram: radial velocity amplitude K, its uncertainty, and the offset of the orbital phase (red to blue crossing yields ϕ₀ = 0) plotted against the separation of the two Gaussians used for the fitting (see text for details). For small separations, the Gaussians trace the central peak of the emission line and the resulting parameters are close to those listed in Table 2. For separations between 16 and 26 Å, the fitting gives stable parameters while the wings are traced. Further outside, the noise increases and the parameters start varying accordingly.