Soft X-ray characteristics of white dwarfs observed by EXOSAT |
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| Authors: | J Heise JAM Bleeker AC Brinkman E Gronenschild F Paerels M Grewing C Wulf-Mathies K Beuerman |
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| Institution: | 1. Laboratory for Space Research, Beneluxlaan 21, 3527 HS Utrecht, The Netherlands;2. Astronomisches Institut, Universität Tübingen, Waldhauser Str. 64, 7400 Tübingen, F.R.G.;3. Max-Planck-Institut für Physik und Astrophysik, 8046 Garching bei München, F.R.G. |
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| Abstract: | EXOSAT has observed 19 hot white dwarfs with alleged strong soft X-ray emission. Positive detection of a large fraction of this sample was obtained, among these practically all hot DA dwarfs. High-resolution spectral data, acquired with the 500 1/mm grating spectrometer, indicates no traces of He in the atmosphere of HZ43, i.e. n(He)/n(H) ? 10?5 at a photospheric temperature of 60000 K (log g = 8). In contrast, the hot DA1 dwarf Feige 24 shows the presence of an appreciable He-abundance (n(He)/n(H) ? 10?3); however no simple homogeneously mixed H/He atmosphere can explain the observed spectral shape. |
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