Difference between the synthetic perturbed spectra of the primary and the corresponding unperturbed spectra showing that the lines of intermediate intensity display the most prominent variations in the “bump” structure. The orbital phases increase from bottom to top with increments of Δφ = 0.1 and starting with φ = 0. Differences are shifted along the vertical axis for clarity. The dotted tracing at the top is the perturbed spectrum at φ = 0.90, scaled and shifted to fit in this figure.