Water and Dust Emission from W Hydrae

We construct a self-consistent model for the wind around W Hydrae by solving the coupled equations describing the hydrodynamics and dust radiative transfer problems. The model matches simultaneously the observed continuum radiation and wind velocity profile. The water line emission is calculated next using the water abundance as the only free parameter, fitted from the Infrared Space Observatory observations of Neufeld et al. and Barlow et al. The gas temperature is determined from a thermal balance calculation that includes water as one of its main components. Our model successfully fits all the observed water lines, resolving a major discrepancy between the modeling results of the two observing teams. The mass-loss rate is 2.3 × 10-6 M☉ yr-1, the water abundance is 1.0 × 10-4, and the ortho-to-para ratio is 1 : 1.3.