8th HEAD Meeting, 8-11 September, 2004
Session 25 X-ray Binaries and White Dwarfs
Poster, Friday, September 10, 2004, 9:00am-10:00pm

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[25.27] Accretion in ultra-compact white dwarf binaries

D. Steeghs (Harvard-Smithsonian Center for Astrophysics), G. Ramsay (MSSL), G. Nelemans (Institute of Astronomy), T. Marsh (University of Warwick), P. Groot (Nijmegen University)

Recently, three accreting binaries have been identified as potentially the most compact binaries known with orbital periods between 5-10 minutes. We briefly discuss the formation and evolution of such ultra-compact white dwarf binaries which are predicted to exist in significant numbers. We present recent optical and XMM-Newton observations of the 10.3 minute system ES Ceti and compare its characteristics with the other proposed ultra-compacts as well as more conventional accreting white dwarfs in cataclysmic variables and AM CVn systems. ES Ceti bears all the hallmarks of being a 10.3 minute binary system that is accreting mainly helium from its degenerate donor stars.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.