  The presence of young stars in the immediate vicinity and strong tidal field
of SgrA* remains unexplained. One currently popular idea for their origin
posits that the stars were bused in by an Intermediate-Mass Black Hole (IMBH)
which has inspiraled into the Galactic Center a few million years ago.
  Yu and Tremaine (2003) have argued that in this case some of the old stars in
the SgrA* cusp would be ejected by hard gravitational collisions with the IMBH.
Here we derive a general expression for the phase-space distribution of the
ejected high-velocity stars, given the distribution function of the stars in
the cusp. We compute it explicitly for the Peebles-Young distribution function
of the cusp, and make a detailed model for the time-dependent ejection of stars
during the IMBH inspiral. We find that (1) the stars are ejected in a burst
lasting a few dynamical friction timescales; if the ejected stars are detected
by Gaia they are likely to be produced by a single inspiral event, (2) if the
inspiral is circular than in the beginning of the burst the velocity vectors of
the ejected stars cluster around the inspiral plane, but rapidly isotropise as
the burst proceeds, (3) if the inspiral is eccentric, then the stars are
ejected in a broad jet roughly perpendicular to the Runge-Lenz vector of the
IMBH orbit. In a typical cusp the orbit will precess with a period of \sim 10^5
years, and the rate of ejection into our part of the Galaxy (as defined by e.g.
the Gaia visibility domain) will be modulated periodically. Gaia, together with
the ground-based follow-up observations, will be able to clock many
high-velocity stars back to their ejection from the Galactic Center, thus
measuring some of the above phenomena. This would provide a clear signature of
the IMBH inspiral in the past 10--20 Myr.
