AAS 207th Meeting, 8-12 January 2006
Session 70 Cataclysmic Variables and Novae
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[70.12] Direct Impact Accretion and Period Decreases in V407 Vul AND RX J0806.3 +1527

X. M. Peng, J. Frank (Louisiana State University)

We study the nature of the Direct Impact Accretion (DIA) phase for semidetached ultra-compact non-magnetic white dwarf binaries. The DIA is very likely to happen following the onset of mass transfer in these low mass binaries due to their ultra-compact orbital size and the trajectory of mass transfer stream. We examine the orbital evolution for the DIA phase and follow the variations in separation, period, mass transfer rate, and X-ray luminosity. We find that following the onset of mass transfer, DIA can create a time window lasting from hundreds of years to thousands of years during which the orbital period decreases. This window may give a possible explanation of the observed period decrease for V407 Vul and RX J0806.3+1527 if they are diskless AM CVn binaries or direct-impact accretors.

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