The density structure of the wind of P Cygni (B1 Ia+).

Near-IR and IRAS observations of the hypergiant P Cygni (B1 Ia⁺) are used to derive the density structure of the wind of P Cygni. The authors find a linear velocity law that is identical to the one derived by Van Blerkom (1978) from an analysis of Balmer line profiles, and differs from the one derived by Barlow and Cohen (1977) based on their analysis of near-IR and radio data. Two models can explain the observed excess at 60 μ: a shell extending from 15 to 50 stellar radii with a density increase of a factor five relative to the quiescent wind, or cold dust with a typical temperature of 30K, situated far away from the star. The dust model can also explain the 100 μ flux if that flux can be attributed to the star and is not a part of the complicated background.