Volume 464, Number 2, March III 2007
|Page(s)||647 - 658|
|Section||Stellar structure and evolution|
|Published online||02 January 2007|
An in-depth study of the pre-polar candidate WX Leonis Minoris
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: email@example.com
2 Department of Physics, University of Warwick, Coventry CV4 7AL, UK
Accepted: 21 November 2006
Optical photometry, spectroscopy, and XMM-Newton ultraviolet and X-ray observations with full phase coverage are used for an in-depth study of WX LMi, a system formerly termed a low-accretion rate polar. We find a constant low-mass accretion rate, yr-1, a peculiar accretion geometry with one spot not accessible via Roche-lobe overflow, a low temperature of the white dwarf, K, and the secondary very likely Roche-lobe underfilling. All this lends further support to the changed view on WX LMi and related systems as detached binaries, i.e. magnetic post-common envelope binaries without significant Roche-lobe overflow in the past. The transfer rate determined here is compatible with accretion from a stellar wind. We use cyclotron spectroscopy to determine the accretion geometry and to constrain the plasma temperatures. Both cyclotron spectroscopy and X-ray plasma diagnostics reveal low plasma temperatures below 3 keV on both accretion spots. For the low-, high-B plasma at the accretion spots in WX LMi, cyclotron cooling dominates thermal plasma radiation in the optical. Optical spectroscopy and X-ray timing reveal atmospheric, chromospheric, and coronal activity at the saturation level on the dM4.5 secondary star.
Key words: stars: individual: WX LMi / stars: magnetic field / X-rays: stars
© ESO, 2007
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