Probing the nucleosynthetic contribution of low-metallicity, low-mass star companions of CEMP stars (2108.01855v1)

Abstract: The observed abundance diversities among the 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$\sim$60,000) and SUBARU/HDS (R$\sim$50,000). We present, for the first time, the elemental abundance results for the objects BD$-$19 132, BD$-$19 290, HE~1304$-$2111, HE~1354$-$2257, and BD+19 3109. Abundances of a few elements are available in literature for HE~1157$-$0518 and HD~202851, we present an update on the abundances of these elements along with new abundance estimates for several other elements. Our analysis confirms the object HD~202851 to be a CH star. While BD$-$19 132, HE~1354$-$2257, and BD+19 3109 are found to be CEMP-s stars, the objects BD$-$19 290, HE~1157$-$0518, and HE~1304$-$2111 are found to belong to CEMP-r/s group. The observed abundance patterns of the three CEMP-r/s stars are well reproduced with the i-process model predictions. While the objects BD+19 3109 and HD~202851 are confirmed binaries, the binary status of the remaining objects are not known. Analysis based on different elemental abundance ratios confirms low-mass former AGB companions for all the objects. Kinematic analysis shows that BD$-$19 290, HE~1157$-$0518, HE~1354$-$2257, and BD+19 3109 belong to the Galactic halo, whereas BD$-$19 132, HE~1304$-$2111, and HD~202851 are members of Galactic thin disk.