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The Interstellar and Circumstellar Environment of White Dwarfs

Published online by Cambridge University Press:  12 April 2016

M.A. Barstow ,
P.D. Dobbie  and
J.B. Holberg
M.A. Barstow
Affiliation:
Department of Physics and Astronomy, University of Leicester, UK
P.D. Dobbie
Affiliation:
Department of Physics and Astronomy, University of Leicester, UK
J.B. Holberg
Affiliation:
Lunar and Planetary Laboratory, University of Arizona, Tucson, USA

Abstract

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We have studied the EUV spectra of 13 DA white dwarfs, observed by the EUVE satellite, paying attention to the possible sources of absorbing material along the lines-of-sight in both the local interstellar medium and in the photospheres of the stars themselves. The range of interstellar column densities seen are consistent with our previous understanding of the local distribution of material. Absorption from interstellar He II is found in the direction of five stars, allowing us to measure directly the He ionization fraction and estimate, indirectly, that of H. The weighted mean ionization fractions along these lines-of-sight are 0.27 ± 0.04 and 0.35 ± 0.1 respectively. Where He II is directly detected, the observed ionization fractions are not correlated with direction or with the volume/column density of material along the line-of-sight. Furthermore, the limits on the amount of He II established in all other directions completely encompass the range of observed values. Indeed, all the data can be consistent with more or less constant He and H ionization fractions throughout the local ISM. However, observation of very hot DA stars, indicating higher He II columns, might contradict this picture if the material is not photospheric or circumstellar.

Type
Part III Observations and Modeling of the Local Bubble and the SXRB
Information
International Astronomical Union Colloquium , Volume 166: The Local Bubble and Beyond , 1997 , pp. 69 - 74
Copyright
Copyright © Springer-Verlag 1998

References

Barstow, M.A., Dobbie, P.D., Holberg, J.B., Hubeny, I., Lanz, T., (1997a): MNRAS, 286, 58 Google Scholar
Barstow, M.A., Holberg, J.B., Hubeny, I., Lanz, T., (1997b): in White Dwarfs, eds. Isern, J., Hernanz, M. and Garcia-Berro, E., Kluwer, 237 Google Scholar
Barstow, M.A., Holberg, J.B., Hubeny, I., Lanz, T., (1997c): in preparation.Google Scholar
Cheng, K.-R, Bruhweiler, F.C., (1990): ApJ, 364, 573 Google Scholar
Frisch, P.C., (1994): Science, 265, 1423 Google Scholar
Gry, C., Lemonon, L., Vidal-Madjar, A., Lemoine, M., Ferlet, R., (1995): A&A, 302, 497 Google Scholar
Lanz, T., Barstow, M.A., Hubeny, L., Holberg, J.B., (1996): ApJ, 473, 1089 Google Scholar
Lyu, C.-H., Bruhweiler, F.C., (1996): ApJ, 459, 216 Google Scholar