Characterizing the High-Velocity Stars of RAVE: The Discovery of a
  Metal-Rich Halo Star Born in the Galactic Disk
  We aim to characterize high-velocity (HiVel) stars in the solar vicinity both
chemically and kinematically using the fourth data release of the RAdial
Velocity Experiment (RAVE). We used a sample of 57 HiVel stars with Galactic
rest-frame velocities larger than 275 km s$^{-1}$. With 6D position and
velocity information, we integrated the orbits of the HiVel stars and found
that, on average, they reach out to 13 kpc from the Galactic plane and have
relatively eccentric orbits consistent with the Galactic halo. Using the
stellar parameters and [$\alpha$/Fe] estimates from RAVE, we found the
metallicity distribution of the HiVel stars peak at [M/H] = -1.2 dex and is
chemically consistent with the inner halo. There are a few notable exceptions
that include a hypervelocity star (HVS) candidate, an extremely high-velocity
bound halo star, and one star that is kinematically consistent with the halo
but chemically consistent with the disk. High-resolution spectra were obtained
for the metal-rich HiVel star candidate and the second highest velocity star in
the sample. Using these high-resolution data, we report the discovery of a
metal-rich halo star that has likely been dynamically ejected into the halo
from the Galactic thick disk. This discovery could aid in explaining the
assembly of the most metal-rich component of the Galactic halo.
