Top left panel: full-resolution LOFAR image contours (white; as shown in the right panel) of SDSS-C4-DR3-3088, overlaid on an exposure-corrected Chandra image in the 0.5−2.0 keV energy band with a total integration time of 17 ks. Top right panel: 150 MHz LOFAR image of SDSS-C4-DR3-3088 (6″ × 6″). The black contours and dashed lines show the (1,2,4,...) × 5 × σ_LOFAR150 and −3 × σ_LOFAR150 levels, respectively, where σ_LOFAR150 = 80 μJy beam⁻¹. Middle left panel: 325 MHz GMRT image (13″ × 7″). The black contours and dashed lines show the (1,2,4,...) × 5 × σ_GMRT325 and −3 × σ_GMRT325 levels, respectively, where σ_GMRT325 = 43 μJy beam⁻¹. Middle right panel: 610 MHz GMRT image (6″ × 4″). The black contours and dashed lines show the (1,2,4,...) × 5 × σ_GMRT610 and −3 × σ_GMRT610 levels, respectively, where σ_GMRT610 = 40 μJy beam⁻¹. Bottom left panel: LOFAR 150 MHz contours (shown in left panel in red) overlaid on an SDSS r-band image of SDSS-C4-DR3-3088. A possible optical counterpart is labelled RG-A. Bottom right panel: LOFAR 150 MHz contours (shown in the top right panel) overplotted on the high-resolution (7″ × 7″) spectral index map of SDSS-C4-DR3-3088.