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Astron. Astrophys. 336, 276-280 (1998)

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Quasi-molecular satellites of Lyman [FORMULA] in ORFEUS observations of DA white dwarfs

D. Koester 1, U. Sperhake 1, N.F. Allard 2, 3, D.S. Finley 4 and S. Jordan 1

1 Institut für Theoretische Physik und Astrophysik der Christian-Albrechts-Universität, D-24098 Kiel, Germany (koester@astrophysik.uni-kiel.de)
2 Observatoire de Paris-Meudon, Département Atomes et Molécules en Astrophysique, F-92195 Meudon Principal Cedex
3 CNRS Institut d'Astrophysique, 98 bis Boulevard Arago, F-75014 Paris, France
4 Eureka Scientific Inc., Oakland, CA, USA

Received 26 March 1998 / Accepted 12 May 1998


Quasi-molecular satellite features of [FORMULA] were first observed in a HUT spectrum of the DA white dwarf Wolf 1346 and interpreted by Koester et al. (1996). In this paper we study the dependence of these features on temperature and surface gravity in 4 additional DA observed with ORFEUS-SPAS II in 1996. For the interpretation we use theoretical atmosphere models which incorporate new profiles for [FORMULA]. These have been calculated by Allard et al. (1998a) including the variation of the transition probability with distance between emitter and perturber. The new calculations for the general line shape, satellite positions and strengths are in very good agreement with the observations.

Key words: stars: white dwarfs – stars: atmospheres – ultraviolet: stars – line: profiles

Send offprint requests to: D. Koester

© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998