The Ultraviolet Spectrum of the High-Field Magnetic Cataclysmic Variable AR Ursae Majoris
Abstract
We have obtained an ultraviolet spectrum covering the range 917-1182 Å of the high-field magnetic cataclysmic variable AR Ursae Majoris when the binary was in its typical low-accretion state. The data reveal an array of deep Zeeman absorption features due to hydrogen Lyα-Lyγ, including several transitions that are normally forbidden but become enabled in the strong electric fields that exist in the atmospheres of highly magnetic white dwarfs. Spectral models indicate a magnetic field strength and structure consistent with that determined from longer wavelength Hubble Space Telescope Space Telescope Imaging Spectrograph UV observations; that is, a dipole of strength ~235 MG offset along its axis by ~0.15 of the stellar radius.
This research is based on observations with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer, which is operated for NASA by Johns Hopkins University under NASA contract NAS 5-32985, and on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysics Research Consortium.- Publication:
-
The Astronomical Journal
- Pub Date:
- October 2004
- DOI:
- 10.1086/423918
- Bibcode:
- 2004AJ....128.1894H
- Keywords:
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- Stars: Novae;
- Cataclysmic Variables;
- Stars: Individual: Constellation Name: AR Ursae Majoris;
- Stars: Magnetic Fields;
- Ultraviolet: Stars;
- Stars: White Dwarfs