Polar (star)

[2] This accretion region covers only a fraction of the WD's surface, but it can contribute half of the system's optical light.

Critically, this asynchronous rotation causes the accretion stream to interact with different magnetic field lines.

[7] The corresponding variations in eclipse depth were shown to depend very strongly on the orientation of the WD's magnetic field with respect to the donor star.

[7] For comparison, in a synchronous polar, the WD does not rotate with respect to the donor star, and the stream always interacts with the same field lines, resulting in a stable accretion geometry.

There is also evidence in each of the four asynchronous polars that the accretion stream is able to travel much deeper into the WD's magnetosphere than in synchronous systems, implying an unusually high rate of mass transfer from the donor star or a low magnetic field strength, but this has not been studied in detail.

[7] Another class of cataclysmic variables with magnetic white dwarfs accreting material from a main sequence donor star are the intermediate polars.