2004/03/01 by G. Israelian, N. G. Shchukina, N. Shchukina +8 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20035785
published as Astron.Astrophys. 419 (2004) 1095-1109 · 16 pages, 15 figures, accepted by Astronomy and Astrophysics
arxiv created 2004/03/01 · openalex publication_date 2004/05/07 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 , 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.