Exploring giant barium stars: ${}^{12}\mathrm{C}{\mathrm{/}}^{13}\mathrm{C}$ ratio and elemental abundances of carbon, nitrogen, and oxygen

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 $\mathit{\text{slow}}$ neutron-capture nucleosynthesis, the $s$-process. As post-interacting 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 ${}^{12}\mathrm{C}{\mathrm{/}}^{13}\mathrm{C}$ 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 $[\mathrm{N}\mathrm{/}\mathrm{F}\mathrm{e}]\sim +0.50$~dex and are moderately correlated with sodium abundances. Except for HD~107541, the entire sample shows $\mathrm{C}\mathrm{/}\mathrm{O}<1$. We found ${}^{12}\mathrm{C}{\mathrm{/}}^{13}\mathrm{C}<20$ for $\sim 80\mathrm{\%}$ of the sampled stars and ${}^{12}\mathrm{C}{\mathrm{/}}^{13}\mathrm{C}>60$ for three objects.