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Published online by Cambridge University Press: 25 September 2002
The aim is to determinethe role and the influence of assumptions concerning bothdynamics and radiative transfer in models of winds and mass loss of evolved stars,when the radiative force on dust grains plays a major role in the structuration of the circumstellar envelope of the star. The flow is described successively using three models coupling the grain and the gas dynamicsin a self-consistent way with radiative transferfor three different approaches of the dynamics:the Position Coupling,the Momentum Coupling and the Full Problem.A complete radiative transfer including multiple scattering,absorption and thermal emission is taken into account to determine the temperature of dust grainswhich in turn governs their thermal emission.The medium is not necessarily optically thin. In all cases, numerical iterations couple dynamics with transfer.Thus two codes are used alternately, starting with an initial profile of radiation pressure,until convergence to a self-consistent solution. This emphasizes the importance of thedrift velocity between the grains and the gas,and the inertia of dust together with hydrodynamics/transfer coupling. When the medium is optically thick, anopaque zone is located at the base of the wind. This zone governs the whole envelope structure. Finally, theexact number of solutions was determined for the one-fluid model.