Exploring Giant Barium Stars:¹²C/¹³C Ratio and Elemental Abundances of Carbon, Nitrogen, and Oxygen^*

Abstract Barium (Ba) stars belong to binary systems that underwent mass-transfer events. As a consequence, their envelopes were enriched with material synthesized in the interiors of their evolved companions via slow neutron-capture nucleosynthesis, the s -process. As postinteracting binaries, Ba stars figure as powerful tracers of the s -process. In this study, we conduct a classical local thermodynamic equilibrium analysis for a sample of 180 Ba giant stars to find complementary insights for the s -process, in form of elemental abundances of carbon, nitrogen, and oxygen, as well as the 12 C/ 13 C ratio. We found carbon abundances systematically larger than those observed in normal giants, with [C/Fe] ratios ranging within from −0.30 to +0.60 dex. As expected, the [C/Fe] ratios increase for lower metallicity regimes and are strongly correlated with the average s -process abundances. Nitrogen abundances have a flat behavior around [N/Fe] ∼ +0.50 dex and are moderately correlated with sodium abundances. Except for HD 107541, the entire sample shows C/O < 1. We found 12 C/ 13 C < 20 for ∼80% of the sampled stars and 12 C/ 13 C > 60 for three objects.