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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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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.