Light curves for the ionising continuum from the central source and for the red and blue BEL wings. The x axis represents time in units of the orbital period, while the y axis represents the normalised flux. Upper panel: Binary scenario with M₁ = 10⁷ M_⊙ and M₂ = 10⁶ M_⊙. The separation is a = 10^−3.9 pc. Lower panel: Single MBH scenario with the same ionising continuum as in the binary case.