GTC/EMIR J-band images of the 21 targets in two epochs and the difference (red positive, blue negative). The two-epoch images are normalised and then stretched on a logarithmic scale to better visualise the faint sources around the central star. White arrow in the difference image indicates the proper motion direction of the star. For clarity, the arrow length is three times the motion during the baseline between the two epochs. All images are centred at the star position at the first epoch with an FoV of 1′ × 1′.