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Preprint 03/06

AGB star intershell abundances inferred from analyses of extremely hot H-deficient post-AGB stars

K. Werner (1), D. Jahn (1), T. Rauch (1), E. Reiff (1), F. Herwig (2), J.W. Kruk (3)

(1) Institut für Astronomie und Astrophysik, Universität Tübingen, Sand~1, 72076 Tübingen, Germany
(2) Los Alamos National Laboratory, Theoretical Astrophysics Group T-6, MS B227, Los Alamos, NM 87545, U.S.A.
(3) Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, U.S.A

To be published in: Proc. "The VIII Torino Workshop on Nucleosynthesis in AGB stars: Constraints on AGB Nucleosynthesis from Observations", edited by C. Abia and I. Dominguez

Abstract. The hydrogen-deficiency in extremely hot post-AGB stars of spectral class PG1159 is probably caused by a (very) late helium-shell flash or a AGB final thermal pulse that consumes the hydrogen envelope, exposing the usually-hidden intershell region. Thus, the photospheric element abundances of these stars allow to draw conclusions about details of nuclear burning and mixing processes in the precursor AGB stars. We compare predicted element abundances to those determined by quantitative spectral analyses performed with advanced non-LTE model atmospheres. A good qualitative and quantitative agreement is found for many species (He, C, N, O, Ne, F, Si) but discrepancies for others (P, S, Fe) point at shortcomings in stellar evolution models for AGB stars.

Preprint (774 kb PDF file including figures)

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