Szkody, Paula Department of Astronomy, University of Washington, Seattle, Washington.
Last reviewed:November 2019
- Accretion disk systems
- Magnetic systems
- Related Primary Literature
- Additional Reading
A type of close binary star system containing a cool star transferring material to its hotter, high-density, degenerate white dwarf companion. The mass transfer results in a large range of observed variability, including cataclysmic events called outbursts, which can increase the brightness of the systems by 2– 10 magnitudes (a logarithmic scale with each magnitude being a factor of 2.5 in brightness) from quiescence, equivalent to a factor of 6–10,000 times in intensity. The specific behavior of each system and the extent and cause of the variability are related to whether the transferred material accumulates in an accretion disk surrounding the white dwarf, or whether it flows in a ballistic stream directly from the cool star to the white dwarf surface. Which of these processes will occur depends on the magnetic field strength of the white dwarf and the separation of the two stars in the binary, properties which are determined during the formation of the system (see illustration). See also: Magnitude (astronomy)
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