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Preprint 03/08

Non-LTE Spectral Analysis of Extremely Hot Post-AGB Stars: Constraints for Evolutionary Theory

Thomas Rauch (1), Klaus Werner (1), Marc Ziegler (1), Lars Koesterke (2), Jeffrey W. Kruk (3)

(1) Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, 72076 Tübingen, Germany
(2) Texas Advanced Computer Center, University of Texas, Austin, TX 78712, USA
(3) Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA

To be published in: Proc. IAU Symp. 252

Abstract. Spectral analysis by means of Non-LTE model-atmosphere techniques has arrived at a high level of sophistication: fully line-blanketed model atmospheres which consider opacities of all elements from H to Ni allow the reliable determination of photospheric parameters of hot, compact stars. Such models provide a crucial test of stellar evolutionary theory: recent abundance determinations of trace elements like, e.g., F, Ne, Mg, P, S, Ar, Fe, and Ni are suited to investigate on AGB nucleosynthesis. E.g., the strong Fe depletion found in hydrogen-deficient post-AGB stars is a clear indication of an efficient s-process on the AGB where Fe is transformed into Ni or even heavier trans iron-group elements. We present results of recent spectral analyses based on high-resolution UV observations of hot stars.
 
Key words: astronomical data bases: miscellaneous, atomic data, line: identification, stars: abundances, stars: AGB and post-AGB, stars: atmospheres, stars: early-type, stars: evolution, (stars:) white dwarfs}

Preprint (291 kb PDF file including figures)
Astrophysics (astro-ph): 0806.1432

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