  Boyajian's star is an apparently normal main sequence F-type star with a very
unusual light curve. The dipping activity of the star, discovered during the
Kepler mission, presents deep, asymmetric, and aperiodic events. Here we
present high resolution spectroscopic follow-up during some dimming events
recorded post-Kepler observations, from ground-based telescopes. We analise
data from the HERMES, HARPS-N and FIES spectrographs to characterise the
stellar atmosphere and to put some constraints on the hypotheses that have
appeared in the literature concerning the occulting elements. The star's
magnetism, if existing, is not extreme. The spots on the surface, if present,
would occupy 0.02% of the area, at most. The chromosphere, irrespective of the
epoch of observation, is hotter than the values expected from radiative
equilibrium, meaning that the star has some degree of activity. We find no
clear evidence of the interstellar medium nor exocoments being responsible for
the dimmings of the light curve. However, we detect at 1-2 sigma level, a
decrease of the radial velocity of the star during the first dip recorded after
the \emph{\emph{Kepler}} observations. We claim the presence of an optically
thick object with likely inclined and high impact parameter orbits that
produces the observed Rossiter-McLaughlin effect.
