The Chemical Compositions of the Extreme Halo Stars HE 0107-5240 and HE 1327-2326 Inferred from Three-dimensional Hydrodynamical Model Atmospheres
Abstract
We investigate the impact of realistic three-dimensional (3D) hydrodynamical model stellar atmospheres on the determination of elemental abundances in the carbon-rich, hyper-iron-poor stars HE 0107-5240 and HE 1327-2326. We derive the chemical compositions of the two stars by means of a detailed 3D analysis of spectral lines under the assumption of local thermodynamic equilibrium (LTE). The lower temperatures of the line-forming regions of the hydrodynamical models cause changes in the predicted spectral line strengths. In particular, we find the 3D abundances of C, N, and O to be lower by about -0.8 dex (or more) than estimated from a 1D analysis. The 3D abundances of iron peak elements are also decreased but by smaller factors (about -0.2 dex). We caution, however, that the neglected non-LTE effects might actually be substantial for these metals. We finally discuss possible implications for studies of early Galactic chemical evolution.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2006
- DOI:
- 10.1086/505643
- arXiv:
- arXiv:astro-ph/0605219
- Bibcode:
- 2006ApJ...644L.121C
- Keywords:
-
- Convection;
- Galaxy: Abundances;
- Stars: Abundances;
- Stars: Atmospheres;
- Stars: Individual: Alphanumeric: HE 0107-5240;
- stars: individual (HE 1327-2326);
- Astrophysics
- E-Print:
- Accepted for publication in ApJL