Reference images of the relic in PSZ2 G121.03+57.02. The white region shows the region used to compute the properties of the relic. Black lines show the 2σ_rms × [1, 2, 4, …] contours from the 50 kpc-taper, compact-source-subtracted LOFAR image from Botteon et al. (2022). Left: Chandra X-ray image. The cyan line scales the distance between the relic position and the cluster centre, as defined in Sect. 2.2. Right: zoom-in of the 50-kpc-taper, compact-source-subtracted LOFAR, centred on the relic. The green line shows the LLS of the relic. Two example lines used to measure the relic width are shown in cyan. The black cross is where we define the relic coordinate.