Tidal disruption events from supermassive black hole binaries
  We investigate the pre-disruption gravitational dynamics and post-disruption
hydrodynamics of the tidal disruption of stars by supermassive black hole
(SMBH) binaries. We focus on binaries with relatively low mass primaries
($10^6M_{\odot}$), moderate mass ratios, and separations with reasonably long
gravitational wave inspiral times (tens of Myr). First, we generate a large
ensemble (between 1 and 10 million) of restricted three-body integrations to
quantify the statistical properties of tidal disruptions by circular SMBH
binaries of initially-unbound stars. Compared to the reference case of a
disruption by a single SMBH, the binary potential induces significant variance
into the specific energy and angular momentum of the star at the point of
disruption. Second, we use Newtonian numerical hydrodynamics to study the
detailed evolution of the fallback debris from 120 disruptions randomly
selected from the three-body ensemble (excluding only the most deeply
penetrating encounters). We find that the overall morphology of the debris is
greatly altered by the presence of the second black hole, and the accretion
rate histories display a wide range of behaviors, including order of magnitude
dips and excesses relative to control simulations that include only one black
hole. Complex evolution persists, in some cases, for many orbital periods of
the binary. We find evidence for power in the accretion curves on timescales
related to the binary orbital period, though there is no exact periodicity. We
discuss our results in the context of future wide-field surveys, and comment on
the prospects of identifying and characterizing the subset of events occurring
in nuclei with binary SMBHs.
