Observed linear polarization of μ Cep on September 6, 2015. The observed Stokes Q is plotted on the left, and Stokes U on the right, as dots in both cases. Continuous lines represent the best fit from the assumed model (green line) with separated contributions from the front disk brightness distribution (red) and the two plumes beyond the limb (black), visible at those wavelengths when they do not constitute the whole contribution to the final fit in green. The upper (orange) profile shows the normalized intensity profile. The vertical dashed lines give the two limiting velocities, V_p and V_*.