LBA observations of HD 93129A at 2.3 GHz. a) Left: at highest angular resolution with an image rms of 0.21 mJy beam^-1 and contour levels shown for −0.6, 0.6 (3σ), 0.7, 0.8, and 0.9 mJy beam^-1. b) Right: a tapered image that increases the weight of the shorter baselines and increases sensitivity to larger scale emission; the image rms is 0.13 mJy beam^-1 and the contour levels are −0.4, 0.4 (3σ), 0.6, 1, 1.4, and 1.8 mJy beam^-1. The synthesized beams are 15 mas × 11 mas and 31 mas × 23 mas, respectively, shown in the bottom righthand corner of the images. The crosses mark the positions of the system components Aa (south) and Ab (north), at the epoch of the radio observations based on the position derived in Sect. 2. North is up and east is to the left.