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With the availability of parallaxes provided by the Tycho-Gaia AstrometricSolution, it is possible to construct the Hertzsprung-Russell diagram (HRD) ofbarium and related stars with unprecedented accuracy. A direct result from thederived HRD is that subgiant CH stars occupy the same region as barium dwarfs,contrary to what their designations imply. By comparing the position of bariumstars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluatetheir masses, provided the metallicity is known. We used an average metallicity[Fe/H] = -0.25 and derived the mass distribution of barium giants. Thedistribution 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 Mgiants used for comparison and is associated with stars located in the redclump. 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 largeradii at the tip of the red giant branch, which may have resulted in an earlybinary interaction. Among barium giants, the high-mass tail is howeverdominated by stars with barium indices of less than unity, based on a visualinspection of the barium spectral line; that is, these stars have a verymoderate barium line strength. We believe that these stars are not genuinebarium giants, but rather bright giants, or supergiants, where the barium linesare strengthened because of a positive luminosity effect. Moreover, contrary toprevious claims, we do not see differences between the mass distributions ofmild and strong barium giants.

Hertzsprung-Russell diagram and mass distribution of barium stars