Potassium abundances in nearby metal-poor stars

Free access article

Issue		A&A Volume 457, Number 2, October II 2006


Page(s)		645 - 650
Section		Stellar atmospheres
DOI		http://dx.doi.org/10.1051/0004-6361:20064909

A&A 457, 645-650 (2006)
DOI: 10.1051/0004-6361:20064909

Potassium abundances in nearby metal-poor stars

H. W. Zhang^{1, 2}, T. Gehren², K. Butler², J. R. Shi^{2, 3} and G. Zhao³

¹ Department of Astronomy, School of Physics, Peking University, Beijing 100871, PR China
e-mail: zhw@bac.pku.edu.cn
² Institut für Astronomie und Astrophysik der Universität München, Scheinerstrasse 1, 81679 München, Germany
³ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China

(Received 25 January 2006 / Accepted 16 June 2006)

Abstract
Aims.The potassium abundances for 58 metal-poor stars are determined using high-resolution spectroscopy. The abundance trends in stars of different population are discussed.
Methods.All abundance results have been derived from NLTE statistical equilibrium calculations and spectrum synthesis methods.
Results.The NLTE corrections are significant (-0.20 to -0.55 dex) and they depend on the effective temperatures and surface gravities. The potassium abundances of thin disk, thick disk and halo stars show distinct trends, such as in the case of the $\alpha$ -elements. [K/Fe] gradually increases with a decrease in [Fe/H] for thin disk stars, [K/Fe] of thick disk stars is nearly constant at [K/Fe] ~ +0.30 dex; halo stars also have nearly constant values of [K/Fe] ~ +0.20 dex.
Conclusions.The derived dependence between [K/Fe] and [Fe/H] is in agreement with the theoretical prediction of published model calculations of the chemical evolution of the Galaxy. The nearly constant [K/Mg] ratio with small scatter suggests that the nucleosynthesis of potassium is closely coupled to the $\alpha$ -elements.

Key words: line: formation -- line: profiles -- stars: abundances -- stars: late-type -- Galaxy: evolution

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