Angular broadening and peculiar velocity of AT2019wey. Left panel: source size vs. frequency (θ = A × ν^β). The 68% confidence intervals of the coefficient A and exponent β are: [43.9, 46.7] and [−2.12, −1.99] for VLBA epoch 1; and [35.1, 45.1] and [−2.43, −1.92] for VLBA epoch 2, respectively. Black: EVN epoch, red: VLBA epoch 1, blue: VLBA epoch 2. Right panel: upper limit on the peculiar velocity of the source set by our proper motion measurement shown by the shaded area. We assumed zero radial velocity, and took into account the errors of the Galactic parameters. The velocities of the stars in the Galactic disc are typically lower than 45 km s⁻¹ (Mignard 2000), and 70 km s⁻¹ is the maximum recoil velocity resulting from typical Blaauw kicks in LMXBs (Nelemans et al. 1999).