RADIATIVE TRANSFER WITHIN A STELLAR ABSORPTION LINE . CONTRIBUTION CURVES OF FINE-ANALYSIS METHODS

Three methods of fine analysis of stellar spectral lines, the formal-solution (F-S), the Planckian-gradient (P-G), and the weight-saturation (W-S), are formally equivalent under the condition of pure absorption or LTE. Comparisons of these methods have been carried out for various model atmospheres of Procyon and the sun and for four representative spectral lines (Table 1). These comparisons were made between curves of growth, line profiles, and related contribution curves. The principal result is that the contribution curves for the three methods and for residual flux are quite different. Small but in some cases not negligible differences in line profiles and curves of growth results from the differences in contribution curves of the three methods, those involving the W-S method being somewhat larger. The P-G method has the advantage of not requiring accurate knowledge of the upper layers of a model atmosphere and normally should be used for fine analyses. The contribution curve for residual flux is a physically significant indicator of stratification in line formation; the others are not. Because this contribution curve has better resolution in atmospheric depth, residual flux should be calculated in inverse fine analyses. © 1969.