Left: Radio/optical centroid position (z_radio/z_opt, top), the resulting radio-optical offset d_app (center, where the error bars correspond to the 1σ uncertainty on the centroid positions, estimated from the effective PSF widths) for two jet powers L_j (see legend), and the apparent opening angle from the radio emission (bottom) as a function of the stellar radius r_c, s and obtained with θ_obs = 5°. The dashed line in the central panel represents the Gaia astrometrical precision. If any, the gray points represent excluded radio/optical centroids, as their positions are downstream of the region where v > 0.9c. Right: Same as left but with θ_obs = 30°.