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Paper: Spin-Up and Spin-Down of Magnetic White Dwarfs in Cataclysmic Variables: Theory vs Long-Term Monitoring
Volume: 334, 14th European Workshop on White Dwarfs
Page: 447
Authors: Andronov, I.L.
Abstract: The evolution of rotation of the magnetic white dwarfs in cataclysmic variables is discussed. The intermediate polars may show spin-up and spin-down, which may be studies using the O-C diagrams. However, having gaps in observations of few year length, it may possible to get an error in cycle counting. Thus annual observations of intermediate polars separated by few months are highly needed, with a total time budget of at least 1-2 nights per object per year. The model of precessing white dwarf is discussed.

In synchronizing polars, there is a weekly-scale beat period between the spin and orbital motion, thus the campaigns similar to the "Noah Project" in BY Cam are needed, when a given star is observed during at least a dozen of nights distributed over the beat phases. Results of such recent observational campaigns are discussed. For the classical polars, the magnetic axis of the white dwarf undergoes cyclic variations both in longitude and latitude with a characteristic full amplitude of ~ 30 degrees and time of few years, as one may see e.g. in AM Her and QQ Vul. Such objects have to be studied polarimetrically or at least photometrically few nights per year.

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