Spectroscopic Orbits for Symbiotic Binaries. III. Eclipses of the Hot Component in RW Hydrae

We analyze optical and ultraviolet spectroscopic observations of the symbiotic star RW Hydrae. This system contains an M2 giant and a hot white dwarf, T_h=8O,OOO K, in an eclipsing binary system with an orbital period of 370.2±0.9d. The component masses are M_g≈0.5-2 M_sun for the red giant and M_h≈O.3-O.6 M_sun for the white dwarf. High-energy photons from the white dwarf ionize the outer atmosphere of the red giant to produce bright emission lines that vary in phase with the orbital period. Densities within the ionized wind range from n_e∼10¹¹ cm^-3 in the inner portion to n_e∼10⁸ cm^-3 in the outer portion.