Modeling of outflowing envelopes of massive evolved stars at arbitrary optical depths
Anton Dorodnitsyn (Space Research Institute)
Bisnovatyi-Kogan G.S. ()
The many observational characteristics of a star with an extended outflowing envelope depend on the physical conditions in the envelope, and can be determined only via self-consistent computations of the evolution of stars taking into account mass loss.
Application of “photospheric” outer boundary conditions can lead to sufficient errors in the solution for the outflowing wind provided that the envelope is geometrically extended.
For evolved supergiants with extended, rarified envelopes, it is important to correctly take into account layers with low optical depths. Addressing these goals we develop
a method that describes a radiation-driven wind that is formed due to absorption of the radiation flux in continuum. It allows to obtain a continuous transition of the solution from regions with large optical depth to the regions of the wind where the optical depth is small.
In order to treat self-consistently regions with small we adopt “zero” boundary conditions posed at infinity. The numerical solution of the two boundary value problem (supersonic part of a wind) is obtained using relaxation technique.