EDP Sciences
Free access
Volume 419, Number 3, June I 2004
Page(s) 1095 - 1109
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20035785

A&A 419, 1095-1109 (2004)
DOI: 10.1051/0004-6361:20035785

Oxygen and magnesium abundance in the ultra-metal-poor giants CS 22949-037 and CS 29498-043: Challenges in models of atmospheres

G. Israelian1, N. Shchukina2, R. Rebolo1, 3, G. Basri4, J. I. González Hernández1 and T. Kajino5

1  Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
2  Main Astronomical Observatory, National Academy of Sciences, 03680 Kyiv-127, Ukraine
3  Consejo Superior de Investigaciones Científcas, Spain
4  Astronomy Department, University of California, Berkeley, California 94720, USA
5  National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan

(Received 2 December 2003 / Accepted 23 February 2004)

We report the results of a non-LTE Fe, O and Mg abundance analysis of the carbon-nitrogen-rich ultra-metal-poor giants CS 29498-043 and CS 22949-037. The abundance of oxygen has been derived from measurements of the oxygen triplet at 7771-5 Å in high resolution spectra obtained with KeckI/HIRES and the forbidden line [O I] 6300 Å detected in the TNG/SARG spectra of CS 29498-043. Detailed non-LTE analysis of Fe lines has provided reliable stellar parameters which, however, do not resolve the oxygen abundance conflict as derived from the O I 7771-5 Å triplet and the [O I] 6300 Å forbidden lines. We obtained the following oxygen abundance: for CS 22949-037 $\mbox{[O/Fe]} =3.13$, 1.95; and for CS 29498-043; [O/Fe] = 3.02, 2.49, based on the O I 7771-5 Å triplet and the [O I] 6300 Å forbidden line, respectively. A similar conflict appears to exist between the forbidden resonance line Mg I 4571 Å and several subordinate lines, such as Mg I 5172 and 5183 Å. Our analysis demonstrates the failure of standard plane-parallel atmosphere models to describe the physical conditions in the line-forming regions of these ultra-metal-poor giants.

Key words: Galaxy: evolution -- nuclear reactions, nucleosynthesis, abundances -- stars: abundances -- stars: late-type -- stars: population III -- stellar atmospheres

Offprint request: G. Israelian, gil@iac.es

SIMBAD Objects

© ESO 2004

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.