Chemical abundances of 10 metal-poor halo stars

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China e-mail: bgs@bao.ac.cn
² Special Astrophysical Observatory, Russian Academy of Sciences, Karachai-Cirkassian Republic, Nizhnij Arkhyz 369167, Russia
³ Department of Astronomy, School of Physics, Peking University, Beijing 100871, PR China

Received: 27 November 2003
Accepted: 3 May 2004

Abstract

We present observations of ten metal-poor halo stars with the metallicity range Fe/H and derive their stellar parameters, acquire some elemental abundances relative to iron and discuss the relation between the abundance ratio and the metallicity. It was found that oxygen abundances are nearly constant at a level of 0.6 dex for our metal-poor halo stars when the non-LTE correction is considered. The α-elements (Mg, Si, Ca and Ti) are overabundant relative to Fe and decrease with increasing metallicity. We also obtained a significant underabundant non-LTE [Na/Fe] ratio from Na i D lines which have a large deviation from the LTE assumption. Scandium is marginally overabundant with respect to iron and tends to decrease with increasing metallicity like the α-elements. A nearly solar value of [Cr/Fe] ratio and underabundant [Mn/Fe] ratio are obtained.