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1.	Collet, Remo, et al. (författare) The Chemical Compositions of the Extreme Halo Stars HE 0107-5240 and HE 1327-2326 Inferred from Three-dimensional Hydrodynamical Model Atmospheres 2006 Ingår i: Astrophysical Journal. - 0004-637X. ; 664:2, s. L121-L124 Tidskriftsartikel (populärvet., debatt m.m.)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.

Collet, Remo, et al. (författare)
The Chemical Compositions of the Extreme Halo Stars HE 0107-5240 and HE 1327-2326 Inferred from Three-dimensional Hydrodynamical Model Atmospheres
2006
Ingår i: Astrophysical Journal. - 0004-637X. ; 664:2, s. L121-L124
Tidskriftsartikel (populärvet., debatt m.m.)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.

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