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Chemical abundances of the metal-poor horizontal-branch stars CS 22186-005 and CS 30344-033 by Caliskan, S.; Caffau, E.; Bonifacio, P.; Christlieb, N.; Monaco, L.; Beers, T. C.; Albayrak, B.; Sbordone, L. is a scholarly article available to read on EtoBox.

What is Chemical abundances of the metal-poor horizontal-branch stars CS 22186-005 and CS 30344-033 about?

We report on a chemical-abundance analysis of two very metal-poor horizontal-branch stars in the Milky Way halo: CS 22186-005 ([Fe/H]=-2.70) and CS 30344-033 ([Fe/H]=-2.90). The analysis is based on high-resolution spectra obtained at ESO, with the spectrographs HARPS at the 3.6 m telescope, and UVES at the VLT. We adopted one-dimensional, plane-parallel model atmospheres assuming local thermodynamic equilibrium. We derived elemental abundances for 13 elements for CS 22186-005 and 14 elements for CS 30344-033. This study is the first abundance analysis of CS 30344-033. CS 22186-005 has been analyzed previously, but we report here the first measurement of nickel (Ni; Z = 28) for this star, based on twenty-two NiI lines ([Ni/Fe]=-0.21$\pm$0.02); the measurement is significantly below the mean found for most metal-poor stars. Differences of up to 0.5 dex in [Ni/Fe] ratios were determined by different authors for the same type of stars in the literature, which means that it is not yet possible to conclude that there is a real intrinsic scatter in the [Ni/Fe] ratios. For the other elements for which we obtained estimates, the abundance patterns in these two stars match the Galactic tren

Author

Caliskan, S.; Caffau, E.; Bonifacio, P.; Christlieb, N.; Monaco, L.; Beers, T. C.; Albayrak, B.; Sbordone, L.

Published

2014

Language

EN