Channel maps of polarised CO J = 2 − 1 emission around the post-AGB star OH 17.7−2.0. The Stokes I total intensity emission is indicated by the solid red contours at 2.5, 5, 10, 20, 40, and 80% of the peak emission (I_CO, peak = 1.04 Jy beam⁻¹). The linearly polarised emission is shown as a greyscale map, and the blue line segments denote the linear polarisation direction when the polarised emission > 5σ_P. The uncertainty on the polarisation direction is thus ≲7°. The segments are scaled to the level of fractional polarisation with the scale indicated in the bottom left panel. The maximum polarisation P_l, max = 4.1%. The panels are labelled with the V_LSR velocity in km s⁻¹, and the beam size is shown in the bottom right panel. The stellar velocity V_LSR, * = 62.0 km s⁻¹. The dashed line indicates the direction of the outflow of OH 17.7−2.0, as in Fig. 1.