cataclysmic variable


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cataclysmic variable

(kat-ă-kliz -mik) (eruptive variable) A close binary star system where one member is a white dwarf, and mass transfer on to the latter causes sudden large and unpredictable changes in brightness. The main classes of cataclysmic variable are classical novae, recurrent novae, dwarf novae, and symbiotic stars. The outbursts of cataclysmic variables are also detected at ultraviolet and X-ray wavelengths; their X-ray output is however much less than that of X-ray transients, which are similar systems where the compact star is a neutron star rather than a white dwarf.

It is generally believed that the progenitors of cataclysmic variables are wide binaries with periods of several months to several years. When the primary evolves and fills its Roche lobe as a giant, mass is lost from it (see equipotential surfaces); this mass forms a common envelope surrounding the core of the giant (a white dwarf) and the companion. Due to frictional drag, the orbit of the immersed binary shrinks until the envelope is ejected forming a bright planetary nebula and a short-period precataclysmic binary.

The distribution of orbital periods of cataclysmic variables displays a very pronounced gap between 2 and 3 hours, known as the period gap. It is widely believed that the gap is caused by the temporary cessation of mass transfer when the orbital period has decreased to three hours (possibly related to changes in the magnetic field of the mass-losing star when its interior becomes fully convective) so that the system has no longer the appearance of a cataclysmic variable.

cataclysmic variable

[¦kad·ə¦kliz·mik ′ver·ē·ə·bəl]
(astronomy)
A star showing a sudden increase in the magnitude of light, followed by a slow fading of light; examples are novae and supernovae. Also known as explosive variable.
In particular, a short-period binary star, one of whose components is a white dwarf star, capable of irregularly timed but recurrent outbursts of brightness by 2 to 10,000.
References in periodicals archive ?
The intensity of hydrogen emission in the Hubble images hinted that several of the stars might qualify as cataclysmic variables.
Cataclysmic variables (CVs) are close binary systems where mass transfer between a white dwarf (WD) and a Roche Lobe-filling late main sequence star takes place.
The observing program was also expanded, adding Cepheid variables, RV Tauri stars, and various eruptive and cataclysmic variables.
During the mission, a network of amateur astronomers using visible-light telescopes will monitor some 275 cataclysmic variables and tell a coordinating group -- the American Association of Variable Star Observers (AAVSO) in Cambridge, Mass.
SDSS J081610.84+453010.2 was first identified spectroscopically as a cataclysmic variable in the first data release from the Sloan Digital Sky Survey (SDSS).
Mike Simonsen, one of the world's leading variable star observers, is development director for the AAVSO and heads its Cataclysmic Variable Section, Chart Team, and Mentor Program.
NASSP colloquium series: Prof Warner: Rapid variations in cataclysmic variable stars (30 April)--Dr Bouchard: The evolutionary state of the local Universe (7 May)--Dr Woudt: Large-scale dynamics of galaxies: From the Great Attractor to the Shapley supercluster (14 May)--Prof Fairall: Mapping the local Universe (10 September)--Prof Warner: Pulsations in white dwarfs (17 September)--Dr Holwerda: Dust extinction effects in spiral galaxies (15 October).
Brad Schaefer, an astronomer at Louisiana State University, has long studied cataclysmic variable stars and other cosmic erupters.
In 2003 Kafka (7) measured the orbital period to be 10.08h, and announced the discovery of an intermittent wind outflow--only the second cataclysmic variable (CV) after BZ Cam to show this phenomenon by this time.
Title: Updates on Two New Cataclysmic Variable Systems: 1RXS J173021.5-055933 and 1RXS J180340.0+401214
Yet it wasn't until August 2005 that a keen-eyed imager noted a cataclysmic variable star just at the nebula's edge.