Abundances of Rb vs. Zr for barium (squares) and extrinsic S stars (filled triangles). The four usual N- and Nb-rich barium stars are shown as open blue squares. Among these, HD 121447 is the most enriched in Zr. The shaded area represents the observed range of Rb and Zr abundances in intermediate-mass AGB stars (van Raai et al. 2012), clearly incompatible with the range measured in barium stars.
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