Abundance Analysis of the Halo Giant HD122563 with Three-Dimensional Model Stellar Atmospheres

Collet, R.
Nordlund, A.
Asplund, M.
Hayek, W.
Trampedach, R.
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We present a preliminary local thermodynamic equilibrium (LTE) abundance analysis of the template halo red giant HD122563 based on a realistic, three-dimensional (3D), time-dependent, hydrodynamical model atmosphere of the very metal-poor star. We compare the results of the 3D analysis with the abundances derived by means of a standard LTE analysis based on a classical, 1D, hydrostatic model atmosphere of the star. Due to the different upper photospheric temperature stratifications predicted by 1D and 3D models, we find large, negative, 3D-1D LTE abundance differences for low-excitation OH and Fe I lines. We also find trends with lower excitation potential in the derived Fe LTE abundances from Fe I lines, in both the 1D and 3D analyses. Such trends may be attributed to the neglected departures from LTE in the spectral line formation calculations.
Comment: 4 pages, 4 figures, contribution to proceedings for Joint Discussion 10 at the IAU General Assembly, Rio de Janeiro, Brazil, August 2009
Astrophysics - Solar and Stellar Astrophysics