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EUVE and ORFEUS Observations of the Cool DO White Dwarf HD 149499 B

Published online by Cambridge University Press:  12 April 2016

R. Napiwotzki ,
S. Jordan ,
S. Bowyer ,
M. Hurwitz ,
D. Koester ,
T. Rauch  and
V. Weidemann
R. Napiwotzki
Affiliation:
Dr. Remeis-Sternwarte, Sternwartstr. 7, 96049 Bamberg, Germany
S. Jordan
Affiliation:
Institut für Astronomie und Astrophysik der Universität, 24098 Kiel, Germany
S. Bowyer
Affiliation:
Center for EUV Astrophysics, 2150 Kittredge Street, University of California, Berkeley, CA 94720-5030, USA
M. Hurwitz
Affiliation:
Center for EUV Astrophysics, 2150 Kittredge Street, University of California, Berkeley, CA 94720-5030, USA
D. Koester
Affiliation:
Institut für Astronomie und Astrophysik der Universität, 24098 Kiel, Germany
T. Rauch
Affiliation:
Institut für Astronomie und Astrophysik der Universität, 24098 Kiel, Germany
V. Weidemann
Affiliation:
Institut für Astronomie und Astrophysik der Universität, 24098 Kiel, Germany

Abstract

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We present the results of a recent spectroscopic investigation of the cool DO white dwarf HD 149499 B in the EUV and FUV ranges. Observations were performed with the spectrograph of the EUVE satellite and the Berkeley EUV/FUV spectrometer of the ORFEUS space experiment. The analysis of the ORFEUS spectrum, performed with a grid of LTE model atmospheres, yielded the basic parameters Teff = 49500 ± 500 K and log g = 7.97 ± 0.08. This result is confirmed by the EUVE spectra. The photospheric hydrogen Lyman lines in the FUV spectrum indicate the presence of hydrogen: log nH/nHe = −0.65 ± 0.12. The implications of this finding for the spectral evolution of white dwarfs are discussed. A check of the LTE assumption was performed by a comparison with NLTE atmospheres calculated for appropriate parameters. The interstellar hydrogen column towards the HD 149499 system amounts to NH = (7 ± 2) · 1018 cm−2.

Type
IV. White Dwarf Structure/Evolution
Information
International Astronomical Union Colloquium , Volume 152: Astrophysics in the Extreme Ultraviolet , 1996 , pp. 241 - 246
Copyright
Copyright © Kluwer 1996

References

Dreizler, S., Werner, K., & Heber, U. 1995, in White dwarfs, ed. Koester, D. & Werner, K., Berlin: Springer Verlag, in pressGoogle Scholar
Edmonds, F.N., Schlüter, H., & Wells, D.C. III, 1976, MmRAS, 71, 271 Google Scholar
Fontaine, G., & Wesemael, F. 1987, in: IAU Colloq. 95, The second conference on faint blue stars, ed. Phillip, A.G.D., Hayes, D.S., & Liebert, J., L. David Press, 319 Google Scholar
Holden, F. 1977, PASP, 89, 588 CrossRefGoogle Scholar
Hurwitz, M. & Bowyer, S. 1995, these proceedingsGoogle Scholar
Ianna, P.A., Rohde, J.R., & Newell, E.B. 1982, ApJ, 259, L71 CrossRefGoogle Scholar
Koester, D., Liebert, J., & Hege, E.K. 1979, A&A, 71, 163 Google Scholar
MacDonald, J., & Vennes, S. 1991, ApJ, 371, 719 CrossRefGoogle Scholar
Napiwotzki, R. 1995a, in White dwarfs, ed. Koester, D. & Werner, K., Berlin: Springer Verlag, In pressGoogle Scholar
Napiwotzki, R. 1995b, A&A, in prepGoogle Scholar
Napiwotzki, R., Hurwitz, M., Jordan, S., Bowyer, S., Koester, D., Weidemann, V., Lampton, M., & Edelstein, J. 1995, A&A, submittedGoogle Scholar
Poulin, E., Wesemael, F., Holberg, J.B., & Fontaine, G. 1989, in White Dwarfs, ed. Wegner, G., Berlin: Springer-Verlag, 144 CrossRefGoogle Scholar
Sion, E.M., Guinan, F., & Wesemael, F. 1982, ApJ, 255, 232 CrossRefGoogle Scholar
Werner, K. 1986, A&A, 161, 177 Google Scholar
Wesemael, F., Green, R.F., & Liebert, J. 1985, ApJ, 58, 379 Google Scholar
Wray, J.D., Parsons, S.B., & Henize, K.G. 1979, ApJ, 234, L187 CrossRefGoogle Scholar