A wind accretion wake in RW Hydrae?

RW Hydrae is an eclipsing detached binary star system, consisting of a mass losing M-giant and a hot white dwarf on circular orbits. We analyze UV observations of RW Hydrae. Approximately at phi = 0.78, clearly unrelated to the primary eclipse, we detect in the UV light curve an event with significantly reduced UV flux. The spectral characteristics of this event indicate Rayleigh scattering due to a high column density of neutral hydrogen in the line of sight to the hot white dwarf. We model this observation in the framework of an accretion wake trailing the white dwarf. This interpretation is analogous to comparable models for zeta Aur systems and X-ray binaries. We find qualitative agreement between our 3D hydrodynamical accretion simulation and the observed UV light curve of RW Hya. Based on observations with the International Ultraviolet Explorer and observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract No. NAS5-26555.