A surprise in the updated list of stellar perturbers of long period
  comets motion
  The second Gaia data release (Gaia DR2) provided us with the precise
five-parameter astrometry for 1.3 billion of sources. As stars passing close to
the Solar System are thought to be responsible for influencing the dynamical
history of long period comets, we update and extend the list of stars that
could potentially perturb motion of these comets. We aim to announce a publicly
available database containing an up to date list of stars and stellar systems
potentially perturbing long period comets motion. We add new objects and revise
previously published lists. Special emphasis was placed on stellar systems.
Discussion on masses estimation is included. Using the astrometry, preferably
from Gaia DR2, augmented with data from other sources, we calculate spatial
positions and velocities for each star. To filter studied objects on the basis
of their minimal heliocentric distances we numerically integrate motion of
stars under the Galactic potential and their mutual interactions. We announce
the updated list of stellar perturbers of cometary motion, including masses of
perturbers along with the publicly available database interface. These data are
ready to be used with the observed long period comets orbits to study an
individual influence of a whole sample of perturbers, or specific stars, on a
dynamical past or future of a specific comet. 147 new perturbers were added in
comparison to the previously published sources. We demonstrate that a new set
of potential perturbers constitute an important tool in studies of cometary
dynamics. The usage of our data significantly changes results of the past and
future comet motion analysis. We point out a puzzling object in our list, star
ALS 9243. The Gaia DR2 astrometry suggests a very close encounter of this star
with the Sun however, its astrophysical parameters result in a completely
different current distance of ALS 9243 and its large mass.
