Chemical analysis of CH stars – III. Atmospheric parameters and elemental abundances

Abstract

Elemental abundances of CH stars can provide observational constraints for theoretical studies on the nucleosynthesis and evolution of low- and intermediate-mass stars. However, available abundance data in literature are quite scanty. In our pursuit to generate a homogeneous data base of elemental abundances of CH stars we have performed a detailed chemical abundance study for a sample of 12 potential CH star candidates based on high-resolution spectroscopy. We present first time abundance analysis for the objects HE0308–1612, CD−281082, HD30443, and HD87853. For the other objects, although limited information is available, detailed chemical composition studies are missing. Our analysis shows CD−281082 to be a very metal-poor object with [Fe/H] = −2.45 and enriched in carbon with [C/Fe] = 2.19. With a ratio of [Ba/Eu] ∼ 0.02 the star satisfies the classification criteria of a CEMP-r/s star. The objects CD−382151 with [Fe/H] = −2.03 and HD30443 with [Fe/H] ∼ −1.68 are found to show the characteristic properties of CH stars. HE0308–1612 and HD87853 are found to be moderately metal poor with [Fe/H] ∼ −0.73; while HE0308–1612 is moderately enhanced with carbon ([C/Fe] ∼ 0.78) and shows the spectral properties of CH stars, the abundance of carbon could not be estimated for HD87853. Among the two moderately metal-poor objects, HD87080 ([Fe/H] = −0.48) shows near solar carbon abundance, and HD176021 ([Fe/H] = −0.63) is mildly enhanced in carbon with [C/Fe] = 0.52. HD176021 along with HD202020 a known binary, exhibit the characteristic properties of CH stars as far as the heavy element abundances are concerned. Five objects in our sample show spectral properties that are normally seen in barium stars.