Illustration of the BLR geometry. Here R_in and R_out are the inner and outer radii of the BLR, while R_BLR is its characteristic radius. L is the angular momentum of the system, l.o.s. is the line of sight to an observer, and finally i is the inclination angle between L and the line of sight. M₁ and M₂ are the masses of the two MBHs, while a is the binary separation. The binary separation and the BLR characteristic radius are not drawn to scale.