CEMP-s and CEMP-rs stars barium isotope ratio

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.