Fit to the He ii 4686 profile using different values for the terminal velocity and the β exponent of the wind velocity law. The mass-loss rate was also varied in each case to obtain a reasonable fit while keeping all other parameters fixed. Red, dotted line: β = 2.0, V_∞ = 1800   km   s^-1, Ṁ = 4.3 × 10^-7   M_⊙   yr^-1 (adopted model); blue, dashed line: β = 1.0, V_∞ = 1800   km   s^-1, Ṁ = 1.1 × 10^-6   M_⊙   yr^-1; orange, dot-dashed line: β = 1.0, V_∞ = 900   km   s^-1, Ṁ = 5.5 × 10^-7   M_⊙   yr^-1. Black: Observed spectrum.