Abstract
Aims. Carbon-enhanced metal-poor (CEMP) stars represent a sizeable fraction of all known metal-poor stars in the Galaxy. Their formation and composition remains a significant topic of investigation within the stellar astrophysics community. Methods. We analysed a sample of low-resolution spectra of 30 dwarf stars, obtained using the visual and near UV FOcal Reducer and low dispersion Spectrograph for the Very Large Telescope (FORS/VLT) of the European Southern Observatory (ESO) and the Gemini Multi-Object Spectrographs (GMOS) at the GEMINI telescope, to derive their metallicity and carbon abundance. Results. We derived C and Ca from all spectra, and Fe and Ba from the majority of the stars. Conclusions. We have extended the population statistics of CEMP stars and have confirmed that in general, stars with a high C abundance belonging to the high C band show a high Ba-content (CEMP-s or -r/s), while stars with a normal C abundance or that are C-rich, but belong to the low C band, are normal in Ba (CEMP-no).
Highlights
The existence of stars with large carbon enhancement was suspected from the very beginning of astronomical spectroscopy
We present an analysis made on a sample of stars observed at low resolution with the visual and near UV FOcal Reducer and low dispersion Spectrograph for the Very Large Telescope (FORS/VLT) of the European Southern Observatory (ESO) and the Gemini Multi-Object Spectrographs (GMOS) at the GEMINI telescope, in the following study, and examine, among other things, their carbon abundances
The Ca abundance has been derived from the Ca II-K line for this plot, for which we estimated an uncertainty of 0.15 dex, while the uncertainty on Fe is the line-to-line scatter, except for the stars for which no clear Fe line is available; in this case, the uncertainty is related to a comparison with synthetic spectra
Summary
The existence of stars with large carbon enhancement was suspected from the very beginning of astronomical spectroscopy. There is currently no evidence that supports an unusually high fraction of binarity in these objects, but only a handful of these objects have radial velocity measurements at this time (e.g. the ultra Fe-poor star by Caffau et al 2016) This would suggest that accretion through binary interaction is probably not the means by which these stars attained their carbon enhancement. These stars would appear to exhibit abundance patterns indicative of the gas cloud from which they formed, making their unusual chemical composition a mystery. We present an analysis made on a sample of stars observed at low resolution with the visual and near UV FOcal Reducer and low dispersion Spectrograph for the Very Large Telescope (FORS/VLT) of the European Southern Observatory (ESO) and the Gemini Multi-Object Spectrographs (GMOS) at the GEMINI telescope, in the following study, and examine, among other things, their carbon abundances
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