Analysis of ultraviolet and extreme-ultraviolet spectra of the DA white dwarf G 191-B2B using self-consistent diffusion models

We present a multi-wavelength spectral analysis of the DA white dwarf G 191 -B2B. The employed atmospheric models account for gravitational settling an d radiative levitation, which are, for the first time, calculated self-cons istently with the atmospheric structure. The resulting spectra can reproduc e; the complete EUVE spectrum and the ultraviolet lines of iron. Some restr ictions regarding the UV lines of other elements (C, N, O, Ni), however, st ill remain. In contrast to homogeneous models, it is not necessary to intro duce additional photospheric or interstellar absorbers to account for the h igh opacity at lambda less than or similar to 230 Angstrom. Abundance profi le changing mechanisms, like mass-loss or accretion, are also not needed.