Spectral index maps obtained between 24 and 43 GHz from VLBA 5 May 2017 (a) and 28 April 2018 (b) observations. The restoring beam size is 0.55 mas ×0.55 mas, that is the circular equivalent-area synthesised beam of VLBA at 24 GHz, drawn as a grey circle in the bottom-right corner. The image has been rotated by −18°. The contours denote the total intensity at 43 GHz and start at 3.5σ rms, increasing in steps of two. The (u, v)-ranges match between all images.