Astron. Astrophys. 336, L33-L36 (1998)

Letter to the Editor

Evidence for helium in the magnetic white dwarf GD 229

S. Jordan ¹, P. Schmelcher ², W. Becken ² and W. Schweizer <sup>3

1</sup> Institut für Theoretische Physik und Astrophysik, D-24098 Kiel, Germany
² Institut für Physikalische Chemie, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany
³ Institut für Astronomie und Astrophysik, Auf der Morgenstelle 10, D-72076 Tübingen, Germany

Received 15 June 1998 / Accepted 27 June 1998

Abstract

The nature of the strong absorption features in the white dwarf GD 229 has been a real mystery ever since it was found to be magnetic in 1974. All attempts to explain the spectrum by line components of hydrogen failed. With the first sets of newly calculated line data for He I in a strong magnetic field we could identify most of the absorption structures in the spectrum with stationary line components in a range of magnetic fields between 300 and 700 MG. This is much lower than previously speculated and is comparable to the highest fields found in hydrogen rich magnetic white dwarfs. The reason for the large number of spectral features in GD 229 is the extreme accumulation of stationary components of transitions in He I in a narrow interval of field strengths.

Key words: stars: white dwarfs stars: magnetic fields stars: individual: GD 229

Send offprint requests to: S. Jordan (e-mail: jordan@astrophysik.uni-kiel.de)

© European Southern Observatory (ESO) 1998

Online publication: July 20, 1998

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