Electromagnetic Emission from Supermassive Binary Black Holes
  Approaching Merger
  We present the first fully relativistic prediction of the electromagnetic
emission from the surrounding gas of a supermassive binary black hole system
approaching merger. Using a ray-tracing code to post-process data from a
general relativistic 3-d MHD simulation, we generate images and spectra, and
analyze the viewing angle dependence of the light emitted. When the accretion
rate is relatively high, the circumbinary disk, accretion streams, and
mini-disks combine to emit light in the UV/EUV bands. We posit a thermal
Compton hard X-ray spectrum for coronal emission; at high accretion rates, it
is almost entirely produced in the mini-disks, but at lower accretion rates it
is the primary radiation mechanism in the mini-disks and accretion streams as
well. Due to relativistic beaming and gravitational lensing, the angular
distribution of the power radiated is strongly anisotropic, especially near the
equatorial plane.
