  With the availability of parallaxes provided by the Tycho-Gaia Astrometric
Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of
barium and related stars with unprecedented accuracy. A direct result from the
derived HRD is that subgiant CH stars occupy the same region as barium dwarfs,
contrary to what their designations imply. By comparing the position of barium
stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate
their masses, provided the metallicity is known. We used an average metallicity
[Fe/H] = -0.25 and derived the mass distribution of barium giants. The
distribution peaks around 2.5 Msun with a tail at higher masses up to 4.5 Msun.
This peak is also seen in the mass distribution of a sample of normal K and M
giants used for comparison and is associated with stars located in the red
clump. When we compare these mass distributions, we see a deficit of low-mass
(1 - 2 Msun) barium giants. This is probably because low-mass stars reach large
radii at the tip of the red giant branch, which may have resulted in an early
binary interaction. Among barium giants, the high-mass tail is however
dominated by stars with barium indices of less than unity, based on a visual
inspection of the barium spectral line; that is, these stars have a very
moderate barium line strength. We believe that these stars are not genuine
barium giants, but rather bright giants, or supergiants, where the barium lines
are strengthened because of a positive luminosity effect. Moreover, contrary to
previous claims, we do not see differences between the mass distributions of
mild and strong barium giants.
