Expanding Atmospheres in OB Supergiants--III: P Cygni

Spectroscopic observations of P Cygni indicate the existence and structure of an extended accelerating envelope about the star. The structure is used as a basis for strong line profile computations, and modified to match computed and observed profiles. The final atmospheric structure resembles that found for three other supergiants and indicates a rate of mass loss from P Cygni of $$5 \times 10^{-4} \,M_{\odot} \,\text{yr}^{-1}.$$