Non-Lte Model Atmospheres. III. a Complete-Linearization Method

In this paper we present a method of solving transfer prob'ems subject to constraints of radiative, hydrostatic, and statistical equilibrium, by using a complete-linearization technique. This approach de- parts rather markedly from the traditional methods, and yields a computational scheme that is stable and strongly convergent. The form of the equations assures that the coupling among all physical variables is fully accounted for self-consistently to first order at each stage of the calculation; convergence is global and quadratic. The constraint equations are included in a particularly transparent way, which allows easy generalization and elaboration. Sample models of pure-hydrogen atmospheres are presented; among these, one includes Ha, H~3, and Pa self-consistently with the continua. Models that were obtained only with great effort by using earlier techniques have been recomputed with no hint of difficulty by using the method described in this paper