Naturally weighted VLBA images of J2331+1129 at 1.6 GHz (left) and 4.9 GHz (right). The intensity colour scales are displayed on the right-hand side of the panels. The lowest contours start at ±3σ rms noise, and the positive levels increase by a factor of 2. Image rms and peak intensity values are shown at the bottom of the panels, and the elliptical Gaussian restoring beams are shown in the lower left corners. The beam sizes are 11.7 mas × 5.7 mas and 4.0 mas × 1.8 mas (FWHM), with major axis position angles of and (measured from north through east) at 1.6 and 4.9 GHz, respectively.