Spectral index distributions of TXS 2013+370. The contour levels are set to 0.5, 1, 2, 4, 8, 16, 32, and 64% Jy/beam of the peak flux density of the highest frequency map in the pair (see Table 1) and represent the total intensity contours. All the images are convolved with a common beam that was set equal to the equivalent circular beam b = (b_maxb_min)^1/2 of the highest frequency, and each frequency pair was aligned using a 2D cross-correlation analysis. Left: Frequency pair of 22-43 GHz. Right: Frequency pair of 43–86 GHz.