X-ray polarization degree, Π_X (top panels) and chromaticity, Π_O/Π_X (bottom panels) as a function of the width of the proton emission region, Δz. In the left panels, the proper number density is assumed to be constant, whereas in the right panels, the magnetization is assumed to be constant. The X-ray polarization degree is Π_X = Π_pp = 2.3, and the optical polarization degree is Π_O = Π_pe = 4.6. The viewing angle is assumed to be θ_obs = 0.1 rad.