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Analysis of ultraviolet and extreme-ultraviolet spectra of the DA white dwarf G 191-B2B using self-consistent diffusion models *
S. Dreizler 1 and
B. Wolff 2
Received 2 February 1999 / Accepted 21 May 1999
We present a multi-wavelength spectral analysis of the DA white dwarf G 191-B2B. The employed atmospheric models account for gravitational settling and radiative levitation, which are, for the first time, calculated self-consistently with the atmospheric structure. The resulting spectra can reproduce the complete EUVE spectrum and the ultraviolet lines of iron. Some restrictions regarding the UV lines of other elements (C, N, O, Ni), however, still remain. In contrast to homogeneous models, it is not necessary to introduce additional photospheric or interstellar absorbers to account for the high opacity at Å. Abundance profile changing mechanisms, like mass-loss or accretion, are also not needed.
Key words: stars: abundances stars: atmospheres stars: evolution stars: individual: G 191-B2B stars: white dwarfs ultraviolet: stars
* Based on observations made with the EUVE Sattelite and with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.
Send offprint requests to: S. Dreizler
Online publication: July 16, 1999