Direct n-body simulations of tidal disruption rate evolution in
  unequal-mass galaxy mergers
  The hierarchical galaxy formation model predicts supermassive black hole
binaries (SMBHBs) in galactic nuclei. Due to the gas poor environment and the
limited spatial resolution in observations they may hide in the center of many
a galaxy. However, a close encounter of a star with one of the supermassive
black holes (SMBHs) may tidally disrupt it to produce a tidal disruption event
(TDE) and temporarily light up the SMBH. In a previous work, we investigated
with direct N-BODY simulations the evolution of TDE rates of SMBHB systems in
galaxy mergers of equal mass. In this work we extend to unequal mass mergers.
Our results show that, when two SMBHs are far away from each other, the TDE
rate of each host galaxy is similar as in an isolated galaxy. As the two
galaxies and their SMBHs separation shrinks, the TDE rate is increasing
gradually until it reaches a maximum shortly after the two SMBHs become bound.
In this stage, the averaged TDE rate can be enhanced by several times to an
order of magnitude relative to isolated single galaxies. Our simulations show
that the dependence of the TDE accretion rate on the mass ratio in this stage
can be well fitted by power law relations for both SMBHs. After the bound SMBHB
forms, the TDE rate decreases with its further evolution. We also find that in
minor mergers TDEs of the secondary SMBH during and after the bound binary
formation are mainly contributed by stars from the other galaxy.
