Pulse phase-averaged normalized Stokes parameters U/I (y-axis) and Q/I (x-axis) over the 2–8 keV energy range. The 1σ, 2σ, and 3σ contours are plotted as concentric circles around the nominal value (continuous and dashed lines, respectively). The gray dotted circle represents loci of constant 1% PD, while radial lines are labeled for specific electric vector position angles (that is, the polarization angle, PA) with respect to north. The phase-averaged PD upper limit is about 2% at 99% c.l.