Evolution of the spectrum of a circumbinary disk evolving together with the central SMBH binary of mass M _c = 10 ⁵  M _☉ and q = 1, starting with an initial semi-major axis 10 ⁻⁴ pc. The disk has M _Edd far from the binary and extends out to 0.1 pc. Its inner radius evolves together with the binary, whose evolutionary track is shown in Figure  6(d). Different curves show the disk spectrum at different times labeled on the panel. Thick lines correspond to a disk self-consistently evolving under the action of the binary torque with no mass flow across the orbit of the secondary allowed (χ = 0). Thin (blue) lines correspond to a constant disk occupying the same region of space. See the text for details.