Revisiting hypervelocity stars after Gaia DR2
  Hypervelocity stars are intriguing rare objects traveling at speeds large
enough to be unbound from the Milky Way. Several mechanisms have been proposed
for producing them, including the interaction of the Galaxy's super-massive
black hole (SMBH) with a binary; rapid mass-loss from a companion to a star in
a short-period binary; the tidal disruption of an infalling galaxy and finally
ejection from the Large Magellanic Cloud. While previously discovered
high-velocity early-type stars are thought to be the result of an interaction
with the SMBH, the origin of high-velocity late type stars is ambiguous. The
second data release of Gaia (DR2) enables a unique opportunity to resolve this
ambiguity and determine whether any late-type candidates are truly unbound from
the Milky Way. In this paper, we utilize the new proper motion and velocity
information available from DR2 to re-evaluate a collection of historical data
compiled on the newly-created Open Fast Stars Catalog. We find that almost all
previously-known high-velocity late-type stars are most likely bound to the
Milky Way. Only one late-type object (LAMOST J115209.12+120258.0) is unbound
from the Galaxy. Performing integrations of orbital histories, we find that
this object cannot have been ejected from the Galactic centre and thus may be
either debris from the disruption of a satellite galaxy or a disc runaway.
