R and I band differential intensity (top), linear polarimetry (middle), and polarization vibration angle (bottom) curves folded in phase using a periodicity of 1.9798 h. Symbols as in Fig. A.2. In the top panel, each data point stands for the average of four individual measurements and its associated dispersion. In the bottom panel, Θ is plotted for P/σ_P ≥ 2.7. Two phases are presented for clarity.