The Effect of Electron Scattering on the Line Spectrum of High-Temperature Stars.

In this paper the problem of the transfer of radiation in an atmosphere of free electrons in thermal motion is considered. Proper allowance is made for the noncoherency of the scattered radiation, but the Compton shifts in frequency of the scattered quanta are ignored. By using a Fourier integral transforma- tion over the frequency, the equation of transfer and the relevant boundary conditions are reduced to sub- sidiary forms. It is shown, further, that the transformed equation of transfer can be solved, in the space of the auxiliary variable, by the standard methods of transfer theory. The explicit solution found in a first approximation is inverted, and the dependence on frequency of the emergent radiation is studied. The final solution to the problem is written down as the sum of two terms: one representing the frac- tion of the incident radiation which emerges without having suffered any scattering process and the other representing the diffuse radiation which has arisen after one or more scattering processes. This diffuse radiation for incident monochromatic light has been evaluated numerically and its values tabulated for four optical thicknesses of the electron atmosphere. The numerical examples studied for hypothetical absorption lines reveal that the main effect of the noncoherency of the electron scattering is to fill the center of the lines with radiation from the neighboring continuum and to produce very extended and shallow wings. Finally, some general remarks are made concerning the relationship between the properties of the solu- tions found and certain characteristics of the line spectrum of high-temperature stars