Extreme Ultraviolet Observations of White Dwarfs
Observations shortward of the hydrogen Lyman limit provide sensitive determinations of stellar temperatures and interstellar absorption. Such data are of particular value in studies of hot white dwarfs, for which a large fraction of the emission occurs in the extreme ultraviolet band (100–1000 Å). Observations of HZ 43 and Feige 24 have been obtained with the Apollo-Soyuz extreme ultraviolet telescope; both stars are copious EUV emitters, with 4 × 10-9 and 3 × 10-9 erg/cm2 sec in the 170–620 Å band respectively. The EUV data combined with optical spectrophotometry, allow their temperatures to be estimated as 80,000 and 60,000 K respectively. The corresponding interstellar neutral hydrogen column densities are ~ 4 × 1018 cm-2.
KeywordsConvection Attenuation Helium Propane Fluoride
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