HE 1327−2326, an Unevolved Star with [Fe/H] < −5.0. I. A Comprehensive Abundance Analysis
Open Access
- 10 March 2006
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 639 (2), 897-917
- https://doi.org/10.1086/497906
Abstract
We present the elemental abundances of HE 1327-2326, the most iron-deficient star known, determined from a comprehensive analysis of spectra obtained with the Subaru Telescope High Dispersion Spectrograph. HE 1327-2326 is either in its main-sequence or subgiant phase of evolution. Its non-LTE-corrected iron abundance is [Fe/H] = -5.45, 0.2 dex lower than that of HE 0107-5240, the previously most iron-poor object known, and more than 1 dex lower than those of all other metal-poor stars. Both HE 1327-2326 and HE 0107-5240 exhibit extremely large overabundances of carbon ([C/Fe] ~ +4). The combination of extremely high carbon abundance with outstandingly low iron abundance in these objects clearly distinguishes them from other metal-poor stars. The large carbon excesses in these two stars are not the result of a selection effect. There also exist important differences between HE 1327-2326 and HE 0107-5240. While the former shows remarkable overabundances of the light elements (N, Na, Mg, and Al), the latter shows only relatively small excesses of N and Na. The neutron-capture element Sr is detected in HE 1327-2326, but not in HE 0107-5240; its Sr abundance is significantly higher than the upper limit for HE 0107-5240. The Li I λ6707 line, which is detected in most metal-poor dwarfs and warm subgiants having the same temperature as HE 1327-2326, is not found in this object. The upper limit of its Li abundance [log < 1.5] is clearly lower than the Spite plateau value. These data provide new constraints on models of nucleosynthesis processes in the first-generation objects that were responsible for metal enrichment at the earliest times. We discuss possible scenarios to explain the observed abundance patterns.This publication has 88 references indexed in Scilit:
- Spectroscopic Studies of Very Metal‐poor Stars with the Subaru High Dispersion Spectrograph. III. Light Neutron‐Capture ElementsThe Astrophysical Journal, 2005
- The Discovery and Analysis of Very Metal-Poor Stars in the GalaxyAnnual Review of Astronomy and Astrophysics, 2005
- Line formation in solar granulationAstronomy & Astrophysics, 2005
- Oxygen Overabundance in the Extremely Iron‐poor Star CS 29498‐043The Astrophysical Journal, 2004
- The evolution of the C/O ratio in metal-poor halo starsAstronomy & Astrophysics, 2004
- A Subaru/High Dispersion Spectrograph Study of Lead (Pb) Abundances in Eights‐Process Element–rich, Metal‐poor StarsThe Astrophysical Journal, 2002
- Chemical Composition of the Carbon-rich, Extremely Metal Poor Star CS 29498−043: A New Class of Extremely Metal Poor Stars with Excesses of Magnesium and SiliconThe Astrophysical Journal, 2002
- Detailed analysis of Balmer lines in cool dwarf starsAstronomy & Astrophysics, 2002
- A search for stars of very low metal abundance. IThe Astronomical Journal, 1985
- Theory of Resonance Broadening of Spectral Lines by Atom-Atom ImpactsPhysical Review B, 1966