Testing the Galactic Centre potential with S-stars
  Two groups of astronomers used the large telescopes Keck and VLT for decades
to observe trajectories of bright stars near the Galactic Centre. Based on
results of their observations the astronomers concluded that trajectories of
the stars are roughly elliptical and foci of the orbits are approximately
coincide with the Galactic Centre position. In a last few years a
self-gravitating dark matter core--halo distribution was suggested by Ruffini,
Arguelles, Rueda (RAR) and this model was actively used in consequent studies.
In particular, recently it has been claimed that the RAR-model provides a
better fit of trajectories of bright stars in comparison to the conventional
model with a supermassive black hole. The dark matter distribution with a dense
core having a constant density as it was suggested in the RAR-model leaves
trajectories of stars elliptical like in Kepler's two-body problem. However, in
this case not the foci of the ellipses coincide with the Galactic Center but
their centers while the orbital periods do not depend on semi-major axes. These
properties are not consistent with the observational data for trajectories of
bright stars.
