Envelope solution in the P_rad–P_gas plane. The colors indicate the logarithm of the Eddington factor Γ, for given P_rad and P_gas, according to the OPAL opacity tables (Iglesias & Rogers 1996), for our pure He model with 23   M_⊙. The envelope solution almost precisely follows a path with Γ = 1. The radii of 2, 4, and 6   R_⊙ within the inflated envelope are indicated. Arrows indicate the slope of the solution, as expected from Eq. (12).