The influence of the secular perturbation of an intermediate-mass
  companion: I. Eccentricity excitation of disk stars at the Galactic center
  There is a dense group of OB and Wolf-Rayet stars within a fraction of a
parsec from the super-massive black hole (SMBH) at the Galactic Center. These
stars appear to be coeval and relatively massive. A subgroup of these stars
orbits on the same plane. If they emerged with low to modest eccentricity
orbits from a common gaseous disk around the central super-massive black hole,
their inferred lifespan would not be sufficiently long to account for the
excitation of their high orbital eccentricity through dynamical relaxation.
Here we analyze the secular perturbation on Galactic Center stars by an
intermediate-mass companion (IMC) as a potential mechanism to account for these
young disk stars' high eccentricity. This IMC may be either an
intermediate-mass black hole (IMBH) or a compact cluster such as IRS-13E. If
its orbital angular momentum vector is anti-parallel to that of the disk stars,
this perturbation would be effective in exciting the eccentricity of stars with
orbital precession rates which resonate with IMC's precession rate. If it
orbits around the SMBH in the same direction as the disk stars, the
eccentricity of the young stars can still be highly excited by the IMC during
the depletion of their natal disk, possible associated with the launch of the
Fermi bubble. In this scenario, IMC's precession rate decreases and its secular
resonance sweeps through the proximity of the young stars. We carry out
numerical simulations with various inclination angles between the orbits of IMC
and the disk stars and show this secular interaction is a robust mechanism to
excite the eccentricity and inclination of some disk stars.
