"Cataclysmic variables (CVs) are close binary systems consisting of a white dwarf and a red-dwarf secondary transferring matter via the Roche lobe overflow."<ref name=Kato>{{ cite journal |author=Kato T|author2=Ishioka R|author3=Uemura M |title=Photometric Study of KR Aurigae during the High State in 2001 |journal=Publ. Astron. Soc. JapanJpn. |volume=54 |issue=6 |date=Dec 2002 |pages=1033–9 |url=http://pasj.asj.or.jp/v54/n6/540624/540624-frame.html |arxiv = astro-ph/0209351 |bibcode = 2002PASJ...54.1033K |doi=10.1093/pasj/54.6.1033}}</ref> Both fusion- and accretion-powered cataclysmic variables have been observed to be [[X-ray]] sources.<ref name=nasa2>{{ cite web |title=Introduction to Cataclysmic Variables (CVs) |url=http://heasarc.gsfc.nasa.gov/docs/objects/cvs/cvstext.html }}</ref> The accretion disk may be prone to [[instability]] leading to [[dwarf nova]] outbursts: a portion of the disk material falls onto the white dwarf, the cataclysmic outbursts occur when the [[density]] and [[temperature]] at the bottom of the accumulated hydrogen layer rise high enough to ignite [[nuclear fusion]] reactions, which rapidly burn the hydrogen layer to helium.
Apparently the only SSXS nonmagnetic cataclysmic variable is V Sge: bolometric luminosity of (1 - 10) x 10<sup>37</sup>, a binary including a blackbody (BB) accretor at T < 80 eV, and an orbital period of 0.514195 d.<ref name=Greiner/>
