Peripheral emission in A781 (blue region of Fig. 2) as observed in the radio band with LOFAR at 143 MHz (left panel) and with the GMRT at 325 MHz (centre panel) and 610 MHz (right panel). Contours are spaced by a factor of 2 starting from 3σ, where σ₁₄₃ = 270 μJy beam⁻¹, σ₃₂₅ = 150 μJy beam⁻¹, and σ₆₁₀ = 120 μJy beam⁻¹. The negative −3σ contours are shown in dashed. The beam sizes are 11.1′′ × 6.5′′ (143 MHz), 10.6′′ × 7.2′′ (325 MHz) and 13.5′′ × 9.8′′ (610 MHz) and are shown in the bottom left corners.