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Diagram of a cataclysmic variable star system

Cataclysmic Variables

Binaries which have a white dwarf and a normal star companion are called cataclysmic variables (CVs). They are typically small -- the entire binary system usually has the size of the Earth-Moon system -- with an orbital period in the range 1-10 hrs. The companion star, a more or less normal star like our Sun, loses material onto the white dwarf (see accretion). Since the white dwarf is very dense, the gravitational potential energy is enormous, and it is converted into X-rays during the accretion process. There are about a million such cataclysmic variables in our Galaxy, but only those close to the Sun (about 100 of them) have been detected in X-rays so far. This is because CVs are fairly faint in X-rays; they are just above the coronal X-ray sources and far below the X-ray binaries in terms of how powerful their X-ray emissions are.

* Take me to Frequently Asked Questions about Binary Systems!

* Take Me to Frequently Asked Questions About White Dwarfs and other Stars!

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