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Preprint 05/01

Equilibrium abundances in hot DA white dwarfs as derived from self-consistent diffusion models

S. L. Schuh (1), S. Dreizler (1), and B. Wolff (2)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Institut für Theoretische Physik und Astrophysik, Universität Kiel, D-24098 Kiel, Germany

To appear in: Astronomy & Astrophysics

Abstract. We present the first analysis of an EUV selected sample of hot DA white dwarfs using a new type of atmospheric models. These models take into account the interplay between gravitational settling and radiative acceleration to predict the chemical stratification from an equilibrium between the two forces while self-consistently solving for the atmospheric structure. In contrast to atmospheric models with the assumption of chemical homogeneity, the number of free parameters in the new models is reduced to the effective temperature and surface gravity alone. The overall good reproduction of observed EUV spectra reveals that these models are able to describe the physical conditions in hot DA white dwarf atmospheres correctly. A comparison with previous analyses highlights the improvements as well as the limits of our new models.

Key words: white dwarfs - Stars: fundamental parameters - Stars: abundances - Stars: atmospheres - Diffusion

Paper (404k gzip'ed Postscript including figures)

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