Analysis of Optical, UV, and EUV Observations of G 191-B2B

Abstract

The major tools for the determination of the photospheric composition of DA white dwarfs are observations in the UV, EUV, and X-ray parts of the electromagnetic spectrum. In the case of G 191-B2B carbon, nitrogen, oxygen, silicon, phosphorus, sulphur, iron, and nickel could be detected in UV and FUV spectra (Bruhweiler & Kondo 1981, Sion et al. 1992, Vennes et al. 1992, Holberg et al. 1994, Vidal-Madjar et al. 1994, Werner & Dreizler 1994, Venues et al. 1996). The presence of these elements results in a strong flux decrease in the EUV and X-ray regions (e.g. Barstow et al. 1993, Dupuis et al. 1995, Wolff et al. 1996).