Searching for correlations in GAIA DR2 unbound star trajectories
  Scattering events with compact objects are expected in the primordial black
hole (PBH) cold dark matter (CDM) scenario due to close encounters between
stars and PBH in the dense environments of dwarf spheroidals. We develop a
Bayesian framework to search for correlations among Milky Way stellar
trajectories and those of globular clusters and dwarf galaxies in the halo, and
other nearby galaxies. We apply the method to a selection of hypervelocity
stars (HVS) and globular clusters from Gaia DR2 catalog, and known nearby
(mostly dwarf) galaxies with full phase-space and size measurements. We report
positive evidence for trajectory intersection $\sim$20-40 Myr ago of up to 2
stars, depending on priors, with the Sagittarius dwarf Spheroidal (dSph) galaxy
when assuming Marchetti et al. (2019) distance estimates. We verify that the
result is compatible with their evolutionary status, setting a lower bound for
the stellar age of $\sim$100 Myr. However, such scattering events are not
confirmed when assuming Anders et al. (2019) distance estimates. We discuss
shortcomings related to present data quality and future prospects for detection
of HVS with the full Gaia catalog and Sagittarius dSph.
