Distribution of the first, second, and third directions extracted from the astrometric variability of the 215 sources in our sample. The directions were derived by assuming a threshold of 0.9 on the model integral (see Fig. 7). The histogram in the left panel shows the primary directions in dark or light blue, the secondary directions in red, and the third directions in green. The histogram in the right panel shows the direction uncertainties with the same color-code. The primary directions are broken into two groups: reliable in dark blue and unreliable in light blue.