Abstract:
The observed abundance diversities among CEMP stars can shed light on the formation and evolution of elements in the early Galaxy. In this work, we present results obtained from a detailed abundance analysis of a sample of seven extrinsic carbon stars. The analysis is based on high-resolution spectra obtained with HCT/HESP (R∼60,000) and SUBARU/HDS (R∼50,000). We present, for the first time, the elemental abundance results for the objects BD−19 132, BD−19 290, HE 1304−2111, HE 1354−2257, and BD+19 3109. Abundances of a few elements are available in the literature for HE 1157−0518 and HD 202851; we present an update on the abundances of these elements along with new abundance estimates for several other elements. Our analysis confirms the object HD 202851 to be a CH star. While BD−19 132, HE 1354−2257, and BD+19 3109 are found to be CEMP-s stars, the objects BD−19 290, HE 1157−0518, and HE 1304−2111 are found to belong to CEMP-r/s group. The observed abundance patterns of the three CEMP-r/s stars are well reproduced with the i-process model predictions. While the objects BD+19 3109 and HD 202851 are confirmed binaries, the binary status of the remaining objects is not known. Analysis based on different elemental abundance ratios confirms low-mass former AGB companions for all the objects. Kinematic analysis shows that BD−19 290, HE 1157−0518, HE 1354−2257, and BD+19 3109 belong to the Galactic halo, whereas BD−19 132, HE 1304−2111, and HD 202851 are members of Galactic thin disk.
