Abundance of barium in the atmospheres of red giants in the Galactic
  globular cluster NGC 104 (47 Tuc)
  Context. While most (if not all) Type I Galactic globular clusters (GGCs) are
characterised by spreads in the abundances of light chemical elements (e.g. Li,
N, O, Na, Mg, Al), it is not yet well established whether similar spreads may
exist in s-process elements as well. Aims. We investigated the possible
difference in Ba abundance between the primordial (1P) and polluted (2P) stars
in the Galactic globular cluster (GGC) 47 Tuc (NGC 104). For this, we obtained
homogeneous abundances of Fe, Na, and Ba in a sample of 261 red giant branch
(RGB) stars which is the largest sample used for Na and Ba abundance analysis
in any GGC so far. Methods. Abundances of Na and Ba were determined using
archival GIRAFFE/VLT spectra and 1D non-local thermodynamic equilibrium (NLTE)
abundance analysis methodology. Results. Contrary to the finding of Gratton et
al. (2013), we did not detect any significant Ba-Na correlation or 2P-1P Ba
abundance difference in the sample of 261 RGB stars in 47 Tuc. This
corroborates the result of D'Orazi et al. (2010) who found no statistically
significant Ba-Na correlation in 110 RGB stars in this GGC. The average
barium-to-iron ratio obtained in the sample of 261 RGB stars, $\langle{\rm
Ba/Fe}_{\rm 1D~NLTE}\rangle = -0.01\pm0.06$, agrees well with those determined
in Galactic field stars at this metallicity and may therefore represent the
abundance of primordial proto-cluster gas that has not been altered during the
subsequent chemical evolution of the cluster.
