The fate of close encounters between binary stars and binary
  supermassive black holes
  The evolution of main sequence binaries that reside in the Galactic Centre
can be heavily influenced by the central supermassive black hole (SMBH). Due to
these perturbative effects, the stellar binaries in dense environments are
likely to experience mergers, collisions or ejections through secular and/or
non-secular interactions. More direct interactions with the central SMBH are
thought to produce hypervelocity stars (HVSs) and tidal disruption events
(TDEs). In this paper, we use N-body simulations to study the dynamics of
stellar binaries orbiting a central SMBH primary with an outer SMBH secondary
orbiting this inner triple. The effects of the secondary SMBH on the event
rates of HVSs, TDEs and stellar mergers are investigated, as a function of the
SMBH-SMBH binary mass ratio. Our numerical experiments reveal that, relative to
the isolated SMBH case, the TDE and HVS rates are enhanced for, respectively,
the smallest and largest mass ratio SMBH-SMBH binaries. This suggests that the
observed event rates of TDEs and HVSs have the potential to serve as a
diagnostic of the mass ratio of a central SMBH-SMBH binary. The presence of a
secondary SMBH also allows for the creation of hypervelocity binaries.
Observations of these systems could thus constrain the presence of a secondary
SMBH in the Galactic Centre.
