An Intermediate Polar (also DQ Herculis Star) is a type of cataclysmic variable binary star system. In most cataclysmic variables, matter from a main-sequence companion star is gravitationally stripped by a white dwarf star in the form of an accretion disk. In intermediate polar systems, the accretion disk is disrupted by the magnetic field of its white dwarf star. Infalling gas from the companion star will form a disk when the matter is still far from the white dwarf, but will follow magnetic field lines in accretion streams when the matter falls closer to the white dwarf. In the transition region between the accretion disk and the accretion stream, infalling gas may also fall as curved sheets called accretion curtains.
The name "intermediate polar" is derived from the strength of the white dwarf's magnetic field, which is between that of non-magnetic cataclysmic variable systems and strongly-magnetic systems. Non-magnetic systems exhibit full accretion disks, while strongly magnetic systems (called polars, or AM Herculis systems) exhibit only accretion streams.
There are 26 confirmed intermediate polar systems as of 14 April 2006. This represents about 1% of the 1,830 total cataclysmic variable systems presented by Downes et al. (2006) in the Catalog of Cataclysmic Variables.
Read more about Intermediate Polar: Physical Properties, Light Curve Periodicities
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