Chemical analysis of CH stars - II: atmospheric parameters and elemental abundances

TL;DR

This study conducts detailed chemical analyses of twelve CH stars using high-resolution spectra to determine their atmospheric parameters and elemental abundances, revealing characteristic heavy element enhancements and contributions from s- and r-process nucleosynthesis.

Contribution

It provides new detailed chemical compositions and atmospheric parameters for a sample of CH stars, including the first abundance analysis of HD 89668, and investigates nucleosynthesis processes.

Findings

Heavy element enhancements observed in several stars.

Wide range of stellar atmospheric parameters estimated.

Evidence of s- and r-process contributions to heavy element abundances.

Abstract

We present detailed chemical analyses for a sample of twelve stars selected from the CH star catalogue of Bartkevicius (1996). The sample includes two confirmed binaries, four objects that are known to show radial velocity variations and the rest with no information on the binary status. A primary objective is to examine if all these objects exhibit chemical abundances characteristics of CH stars, based on detailed chemical composition study using high resolution spectra. We have used high resolution (R ~ 42000) spectra from the ELODIE archive. These spectra cover 3900 to 6800 Angstrom in the wavelength range. We have estimated the stellar atmospheric parameters, the effective temperature Teff, the surface gravity log g, and metallicity [Fe/H] from LTE analysis using model atmospheres. Estimated temperatures of these objects cover a wide range from 4200 K to 6640 K, the surface gravity from 0.6 to 4.3 and metallicity from -0.13 to -1.5. We report updates on elemental abundances for several heavy elements, Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu and Dy. For the object HD 89668 we present the first abundance analyses results. Enhancement of heavy elements relative to Fe, a characteristic property of CH stars is evident from our analyses in case of four objects, HD 92545, HD 104979, HD 107574 and HD 204613. A parametric model based study is performed to understand the relative contributions from the s- and r-process to the abundances of the heavy elements.