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Helium Abundance in the Photospheres of Hot Da White Dwarfs

Published online by Cambridge University Press:  12 April 2016

J. B. Holberg ,
K. Kidder ,
J. Liebert  and
F. Wesemael
J. B. Holberg
Affiliation:
Lunar and Planetary Laboratory,University of Arizona Tucson, Arizona 85721
K. Kidder
Affiliation:
Lunar and Planetary Laboratory,University of Arizona Tucson, Arizona 85721
J. Liebert
Affiliation:
Steward Observatory,University of Arizona Tucson, Arizona 85721
F. Wesemael
Affiliation:
Département de Physique and Observatoire du,Mont Mégantic Université de Montréal

Abstract

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We have used optical and UV spectroscopy to determine He abundances and upper limits to He abundances in the photospheres of a selected sample of very hot hydrogen-rich white dwarfs. He abundances in the range log(He/H) -3 to -1.5 are observed in several of these DAs and upper limits of -3 determined for the remainder. In apparent contradiction to the relatively large He abundances inferred from soft X-ray observations for the hot DA G191 B2B, we find no evidence of He in the optical and UV.

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 114: White Dwarfs , 1989 , pp. 188 - 193
Copyright
Copyright © Springer-Verlag 1989

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