Abstract

We have obtained an ultraviolet spectrum covering the range 917–1182 A 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.

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