Balmer Emission Lines in T Tauri-Like Decelerating Flows.

The star and envelope properties are chosen to approximate T Tauri star conditions. The Sobolev approximation is used to solve the radiative transfer problem in the envelope and the application of this technique to decelerating atmospheres is discussed. A ten-level model hydrogen atom including forty-five line transitions is utilized and the effects of changes in the adopted collisional cross sections and recombination rates are determined. The details of the solutions of the hydrogen level populations are presented for a range of envelope conditions. The effects of changes in the effective temperature of the central star, the electron temperature of the envelope, the stellar mass loss ratio and the initial flow velocity in the decelerating envelope are discussed. The Balmer line profiles are computed by integrations along surfaces of equal line of sight velocity. Changes in emission line strengths and shapes and the behavior of the Balmer decrement were determined for a range of envelope conditions.