VLA radio maps of J1356+10. Same as Fig. A.1. Contour levels for the B-configuration data start at 3.5, 4.5, 5.5σ and then increase in steps of , with σ ∼ 37 μJy beam⁻¹ the local rms noise. At these low levels, image artefacts are visible around the strong core. Negative contours are shown at the same level in grey. Contours of the A-configuration data start at 450 μJy beam⁻¹ and increase with factor .