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The Magnetospheric Boundary in Cataclysmic Variables

Hellier, Coel

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Abstract

The magnetic cataclysmic variables (MCVs) present a wealth of observational diagnostics for studying accretion flows interacting with a magnetosphere. Spin-period pulsations from the rotation of the white dwarf are seen in optical light, in the UV and X-ray bands, and in polarimetry, and modelling these can constrain the size and location of the accretion footprints on the white-dwarf surface. Tracing these back along field lines can tell us about the transition region between the stream or disk and the magnetosphere. Further, optical emission lines give us velocity information, while analysis of eclipses gives spatial information. I discuss MCVs (particularly FO Aqr, V405 Aur, XY Ari and EX Hya, but also mentioning PQ Gem, GK Per, V2400 Oph, HT Cam, TX Col, AO Psc, AE Aqr, WZ Sge, V1223 Sgr and DQ Her), reviewing what observations tell us about the disk-magnetosphere boundary. The spin-period variations are caused by a mixture of geometric effects and absorption by the accretion flow, and appear to show that the accretion disk feeds onto field lines differently in different systems, being sometimes along field lines ahead of the magnetic pole and sometimes behind the pole. During outbursts, when the accretion flow increases by orders of magnitude, the disk pushes the magnetosphere inwards, and appears to feed field lines over a much greater range of magnetic azimuth. The non-equilibrium outburst behaviour shows an even richer phenomenology than in quiescence, adding DNOs and QPOs into the mix.

Journal Article Type Conference Paper
Conference Name EPJ Web of Conferences
Acceptance Date Jan 8, 2014
Publication Date Jan 8, 2014
Publicly Available Date Mar 28, 2024
Journal EPJ Web of Conferences: The Space Photometry Revolution – CoRoT Symposium 3, Kepler KASC-7 Joint Meeting
Print ISSN 2100-014X
Publisher Società Italiana di Fisica
Peer Reviewed Peer Reviewed
Volume 64
DOI https://doi.org/10.1051/epjconf/20136407001
Publisher URL http://www.epj-conferences.org/articles/epjconf/abs/2014/01/epjconf_mag2013_07001/epjconf_mag2013_07001.html

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