On modeling radiationdriven envelopes at arbitrary optical depths
Abstract
We consider stationary outflowing stellar envelopes accelerated by radiation pressure. Making use of solutions of the transfer equation in the Eddington approximation, we derive relations for pressure, radiation energy density, and radiative energy flux at arbitrary optical depth tau . These relations are used in the equations of radiative hydrodynamics, which can be solved numerically. The solution proceeds through a singular point, where the velocity is equal to the isothermal sound speed, and satisfies zero temperature and pressure boundary conditions at infinity. A sample calculation is performed for a constant opacity and molecular weight. We argue that, with realistic opacity tables and thermodynamic functions which take into account variable ionization states and in conjunction with selfconsistent evolutionary calculations, our method for constructing outflowing envelopes will provide unambiguous massloss rates for massive stars in yellow and red supergiant stages. Advantages of this approach are discussed in comparison with previously used methods.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 April 1999
 Bibcode:
 1999A&A...344..647B
 Keywords:

 HYDRODYNAMICS;
 RADIATIVE TRANSFER;
 STARS: CARBON;
 STARS: MASSLOSS