RADIATION-TRAPPING IN CYLINDRICAL AND SPHERICAL GEOMETRIES

We solve the Holstein radiation-trapping equation numerically for cylindrically and spherically symmetric geometries. For Doppler and Lorentz lineshapes, we give analytical fitting equations for the trapping factors and for the shapes of the 10 lowest-order modes. For Voigt profiles, we modify the classical Walsh-interpolation formula so that it is now applicable at all opacities and for all modes. The results are checked by Monte Carlo simulation and by comparison with existing approximations. Our fits and interpolations yield 2-20% accuracy.