Initial 1D and resulting 〈2D〉 gas density [in g cm⁻³] (top) and temperature [in K] (bottom) structure for the O4 model as a function of modified radius x = 1 − R₀/r, with R₀ as the lower boundary radius. The ‘red dash-dotted’ line is the 〈2D〉 photosphere and the ‘blue dash-dotted’ is the 1D photosphere. The cyan dash-dotted curve is produced using FASTWIND as described with specifications in Sect. 2.3.