Enhancement (v sin i_⋆, λ) grid for the best-fit value of b together with the best-fit 1σ 2D Gaussianmodel (dashed). For each (v sin i_⋆, λ, b) triple the grid values were constructed by shifting the model and shadow bump a corresponding amount, such that the model shadow bump is centered at zero. This was followed by collapsing the shifted data shadow in intensity space. The contour signal at a specific (v sin i_⋆, λ, b) value is then the resulting value of the collapsed shifted data shadow at a velocity of zero.