Polarization angle of the limb, plotted for multiple different values of a and ϕ. The terminal Lorentz factor is fixed at γ_∞ = 2.5. In all cases, we have γ_∞ < csci, so the swing appears on the receding edge. The blue stars denote the prediction of Equation (49) for the location of ﹩{\tilde{R}}_{{\rm{limb}}}﹩ and hence ﹩{\tilde{\beta }}_{{\rm{limb}}}﹩ (the point at which f^R = 0).