Slices of the marginalised posterior probability of the (v_e, R₀, ⟨M⟩) parameter space (three-dimensional after the marginalisation over the angle of v_e using Eq. (17)) for each of the three models described in Sect. 4. Model LF: light curves simulated without reverberation and fitted only to the low-frequency data, i.e. up to 1/750 days⁻¹, which corresponds to the same frequency cut as in Morgan et al. (2012). Model FF: same simulations are fitted to the full frequency range, i.e. up to 1/100 days⁻¹. Model RFF: light curves are now simulated with reverberation (f_BLR = 0.432 ± 0.036, σ_DRW = 55 and R_BLR = R_BLRMK11) and the full observed frequency range up to 1/100 days⁻¹ is considered. The solid line corresponds to R_MK11, the estimate of Mosquera & Kochanek (2011), the ellipse represents the (v_e, R₀) measurement interval from Morgan et al. (2012). The coloured contours encapsulate [10–100]% of the probability volume and are projected in each of the displayed slices. We note that our probability densities are not scaled by the evidence and therefore cannot be compared across different models.