Theoretical profiles of balmer lines in the spectra of stars with moving envelopes with allowance for spectral dependence of the hydrogen absorption coefficient

Abstract

A method for constructing theoretical profiles of emission lines in the spectra of stars with moving envelopes with allowance for a fre- quency dependence of the atomic absorption coefficient is described. The results of calculations for Voigt, Doppler, and rectangular pro- files of the absorption coefficient are compared. The example of the construction of the profile of H a for a disk envelope having differ- ent orientations relative to the observer is given. distribution of the radiating matter with respect to the radial velocities. The profiles were constructed using a rectangular profile of the hydrogen absorption coefficient in the lines. A series of models of envelopes with different sets of basic parameters describing the structure and kinematics, and also the main properties of the star, was considered. Comparison of the theoretical profiles of the lines H~_7 with the observed profiles showed that in a number of cases perfectly satisfactory agreement can be obtained. However, there are conditions under which the method becomes invalid or at least only partly valid. Three cases can be distinguished: i. The most general case is when a) an envelope is opaque in the continuum at the frequencies of the investigated lines, or b) the velocity gradient in an envelope is not sufficiently high for the two conditions described above, the basis of the calculations, to hold. Then the problem requires simultaneous solution of the stationarity equations for the energy levels and the equation of radiative transfer in the lines over the complete envelope. The problem is rather complicated and requires a special treatment that goes beyond the scope of the present paper. 2. The velocity gradient is not yet sufficiently large for one to be able to use Sobolev's method to calculate the level populations but is already too small for the real profile of the hydrogen absorption coefficient to have no influence on the form of the line profiles.