Mass loss in alpha Cygni: synthetic H-alpha profiles

Observations by Inoue show that the Hα profile in α Cygni (A2 Ia) is characterized by shallow, shortward-shifted absorption, with an intensity longward of the rest wavelength that is at or above the continuum level. We interpret these characteristics in terms of a model stellar envelope that is spherically symmetric, expands with monotonically increasing velocity, and obeys mass flux continuity from the thermally controlled regime below the photosphere to the layers outside the line formation zone of Hα. The principal free variables are the mass loss rate, the wind velocity law, and the Doppler broadening velocity law. The statistical equilibrium equations are solved for a six-level hydrogen atom in the comoving frame of the fluid, with the resonance transformations included explicitly, and with the intrinsic line profile assumed to be Gaussian.rofiles from Inoue's class b (those with smaller central intensity in the absorption feature). The present models cannot, however, match the shallower absorption features in class a