Top panel: value of Γ versus scaled radius-coordinate for 7 (non-consecutive) hydrodynamic iterations over the complete run. The starting structure (yellow) relaxes to the final converged structure (dark blue). Bottom panel: colour map of log (f_err) for all hydrodynamic iterations; on the abscissa is hydrodynamic iteration number and on the ordinate scaled wind velocity. The pluses indicate the location of for each iteration, the dashed lines the limits between which is computedand the dash-dotted line the location of the sonic point.