Polarization degree versus the cosine of the inclination angle μ are shown after integrating the signal in the IXPE operating band (2–8 keV), for the 2013 (top panels) and 2014 (bottom panels) cases and for both extended slab and spherical geometries. Left panels show simulations in which the input kT_e and τ correspond to best fit values, while we took into account statistically equivalent parameters (i.e. corresponding to relative minima in the fits, see Fig. 3) in the right panels.