  Hierarchical structure formation inevitably leads to the formation of
supermassive binary black holes (BBHs) with a sub-parsec separation in galactic
nuclei. However, to date there has been no unambiguous detection of such
systems. In an effort to search for potential observational signatures of
supermassive BBHs, we performed high-resolution smoothed particle hydrodynamics
(SPH) simulations of two black holes in a binary of moderate eccentricity
surrounded by a circumbinary disk. Building on our previous work, which has
shown that gas can periodically transfer from the circumbinary disk to the
black holes when the binary is on an eccentric orbit, the current set of
simulations focuses on the formation of the individual accretion disks, their
evolution and mutual interaction, and the predicted radiative signature. The
variation in mass transfer with orbital phase from the circumbinary disk
induces periodic variations in the light curve of the two accretion disks at
ultraviolet wavelengths, but not in the optical or near-infrared. Searches for
this signal offer a promising method to detect supermassive BBHs.
