Hostname: page-component-84b7d79bbc-dwq4g Total loading time: 0 Render date: 2024-07-25T08:02:39.013Z Has data issue: false hasContentIssue false
  • English
  • Français

The Composition and Structure of White Dwarf Atmospheres Revealed by Extreme Ultraviolet Spectroscopy

Published online by Cambridge University Press:  12 April 2016

Martin A. Barstow ,
Ivan Hubeny ,
Thierry Lanz ,
Jay B. Holberg  and
Edward M. Sion
Martin A. Barstow
Affiliation:
Department of Physics and Astronomy, University of Leicester, University Road, Leicester LEI 7RH, UK
Ivan Hubeny
Affiliation:
Universities Space Research Association NASA/GSFC, Greenbelt, MA 20711, USA
Thierry Lanz
Affiliation:
Universities Space Research Association NASA/GSFC, Greenbelt, MA 20711, USA
Jay B. Holberg
Affiliation:
Lunar and Planetary Laboratory, University of ArizonaTucson, AZ 85721, USA
Edward M. Sion
Affiliation:
Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085, USA

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The ROSAT and EUVE all-sky surveys have resulted in an important change in our understanding of the general composition of hydrogen-rich DA white dwarf atmospheres, with the photospheric opacity dominated by heavy elements rather than helium in the hottest stars (T > 40, 000 K). Most stars cooler than 40,000 K have more or less pure H atmospheres. However, one question, which has not been resolved, concerned the specific nature of the heavy elements and the role of helium in the hottest white dwarfs. One view of white dwarf evolution requires that H-rich DA stars form by gravitational settling of He from either DAO or He-rich central stars of planetary nebulae. In this case, the youngest (hottest) DA white dwarfs may still contain visible traces of He. Spectroscopic observations now available with EUVE provide a crucial test of these ideas. Analysis of data from the EUVE Guest Observer programme and EUVE public archive allows quantitative consideration of the sources of EUV opacity and places limits on the abundance of He which may be present.

Type
IV. White Dwarf Structure/Evolution
Information
International Astronomical Union Colloquium , Volume 152: Astrophysics in the Extreme Ultraviolet , 1996 , pp. 203 - 210
Copyright
Copyright © Kluwer 1996

References

Barstow, M.A. et al. 1993, MNRAS, 264, 16 Google Scholar
Barstow, M.A. et al. 1994, MNRAS, 267, 653 CrossRefGoogle Scholar
Barstow, M.A., Holberg, J.B. & Koester, D. 1994a, MNRAS, 268, L35 CrossRefGoogle Scholar
Barstow, M.A., Holberg, J.B. & Koester, D. 1994b, MNRAS, 270, 516 Google Scholar
Barstow, M.A., Holberg, J.B. & Koester, D. 1995, MNRAS, in pressGoogle Scholar
Barstow, M.A. & Sion, E.M. 1994, MNRAS, 271, L52 Google Scholar
Bergeron, P., et al. 1994, ApJ, 432, 305 Google Scholar
Fleming, T.A., Liebert, J. & Green, R.F. 1986, ApJ, 308, 176 CrossRefGoogle Scholar
Holberg, J.B. et al. 1995, ApJ, in pressGoogle Scholar
Hubeny, I. 1988, Comp. Phys. Comm., 52, 103 CrossRefGoogle Scholar
Hubeny, I. & Lanz, T. 1992, A&A, 262, 501 Google Scholar
Hubeny, I. & Lanz, T. 1995, ApJ, 439, 875 CrossRefGoogle Scholar
Lanz, T. & Hubeny, T. 1995, ApJ, 439, 905 CrossRefGoogle Scholar
Marsh, M.C. et al. 1995, in Proceedings of the 9th European Worshop on White Dwarfs, ed. Koester, D. & Werner, K., Lecture Notes in Physics, Springer, in pressGoogle Scholar
Napiwotzki, R. 1993, A&A, 278, 478 Google Scholar
Rumph, T., Bowyer, S. & Vennes, S. 1994, AJ, 107, 2108 Google Scholar
Vennes, S., Pelletier, C., Fontaine, G., & Wesemael, F. 1988, ApJ, 331, 876 Google Scholar