2006•arXiv (Cornell University)Open access
AGB star intershell abundances inferred from analyses of extremely hot\n H-deficient post-AGB stars
K. Werner, David Jahn, T. Rauch, E. Reiff, Falk Herwig, J. W. Kruk
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Abstract
The hydrogen-deficiency in extremely hot post-AGB stars of spectral class\nPG1159 is probably caused by a (very) late helium-shell flash or a AGB final\nthermal pulse that consumes the hydrogen envelope, exposing the usually-hidden\nintershell region. Thus, the photospheric element abundances of these stars\nallow to draw conclusions about details of nuclear burning and mixing processes\nin the precursor AGB stars. We compare predicted element abundances to those\ndetermined by quantitative spectral analyses performed with advanced non-LTE\nmodel atmospheres. A good qualitative and quantitative agreement is found for\nmany species (He, C, N, O, Ne, F, Si) but discrepancies for others (P, S, Fe)\npoint at shortcomings in stellar evolution models for AGB stars.\n
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