Journal Article

The evolutionary state of short-period magnetic white dwarf binaries

E. Breedt, B. T. Gänsicke, J. Girven, A. J. Drake, C. M. Copperwheat, S. G. Parsons and T. R. Marsh

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 423, issue 2, pages 1437-1449
Published in print June 2012 | ISSN: 0035-8711
Published online June 2012 | e-ISSN: 1365-2966 | DOI:
The evolutionary state of short-period magnetic white dwarf binaries

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We present phase-resolved spectroscopy of two new short-period low accretion rate magnetic binaries, SDSS J125044.42+154957.3 (Porb= 86 min) and SDSS J151415.65+074446.5 (Porb= 89 min). Both systems were previously identified as magnetic white dwarfs from the Zeeman splitting of the Balmer absorption lines in their optical spectra. Their spectral energy distributions exhibit a large near-infrared excess, which we interpret as a combination of cyclotron emission and possibly a late-type companion star. No absorption features from the companion are seen in our optical spectra. We derive the orbital periods from a narrow, variable Hα emission line which we show to originate on the companion star. The high radial velocity amplitude measured in both systems suggests a high orbital inclination, but we find no evidence for eclipses in our data. The two new systems resemble the polar EF Eri in its prolonged low state and also SDSS J121209.31+013627.7, a known magnetic white dwarf plus possible brown dwarf binary, which was also recovered by our method.

Keywords: binaries: close; stars: individual: SDSS J125044.42+154957.3; stars: individual: SDSS J151415.65+074446.5; stars: magnetic field; novae, cataclysmic variables; white dwarfs

Journal Article.  10993 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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