Posterior probability densities of the radius of the Mg II or Hα BLR. The BLR radius is expressed in Einstein radius units. It was computed with ℳ = 0.3 ℳ_⊙, r_E = 9.7, 9.2, 8.1, 10.1, 11.5 light-days for J1131, J1226, J1355, J1339, and HE0435, respectively. Left panels: Probability densities of the half-light radius, r_1/2, obtained with two magnification maps characterized by low (black) and high (blue) fractions of compact objects, and after marginalizing over the two maps (red). Middle panels: Same as the left panels but for the flux-weighted mean radius, r_mean. Right panels: Comparison of the probability densities, marginalized over the two maps, of the half-light radius (red and blue curves) and the flux-weighted mean radius (magenta and black curves), computed with constraints from the continuum source magnification (red and magenta curves) and without this constraint (blue and black curves).