We present a spectroscopic analysis of ten carbon enhanced metal-poor (CEMP) stars of type CEMP-s and CEMP-rs and determine their non-local thermodynamic equilibrium (NLTE) abundances of Ba and Eu, as well as the fractions of the odd Ba isotopes (F_odd_). Determination of F_odd_ in stars provides unambiguous information about the s-process contribution to their total Ba abundance. We aim to obtain observational constraints on the enrichment scenarios of CEMP-rs stars. The Ba abundances inferred from the resonance BaII 4554 and 4934{AA} lines depend on the adopted Ba isotope mixture. We perform calculations for different F_odd_ from 0.1 to 1.0 and determine the corresponding abundances from the BaII resonance lines in each sample star. In addition, we determine the Ba abundances from the BaII subordinate lines, which are almost independent of F_odd. We then compare the Ba abundances derived from the subordinate lines with those from the BaII resonance lines. We found different F_odd values in CEMP-s and CEMP-rs stars. CEMP-s stars exhibit F_odd_=0.05_-0.03_^+0.07^, 0.17_-0.14_^+0.63^, 0.19_-0.14_^+0.50^, and 0.19_-0.12_^+0.33^. The obtained values agree, within the error bars, with the s-process F_odd_=0.10 and the solar F_odd_=0.18. Although the uncertainties are large, in three of four stars, the possibility of Ba isotopes origin in a pure r-process with F_odd_=0.75 can be excluded. CEMP-rs stars show F_odd_=0.34_-0.21_^+0.55^, 0.36_-0.14_^+0.23^, 0.44_-0.22_^+0.43^, 0.53_-0.38_^+0.47^, and 0.57_-0.31_^+0.43^, which are higher compared to those in CEMP-s stars. Although the uncertainties are large, in four of five stars, the possibility of a pure s-process origin for the Ba isotopes can be excluded. The obtained values agree, within the error bars, with the predicted i-process F_odd_=0.6 to 0.8. Our analysis of CEMP-rs stars with [Ba/Eu]>0 argues that their [Ba/Eu] and F_odd_ cannot be jointly explained by a mixture of material produced by the r- and s-processes. The obtained results argue that the i-process is responsible for the chemical composition of these CEMP-rs stars.

Cone search capability for table J/A+A/704/A103/stars (star)