Detection of extended Hα emission in the INT/WFC observations in the narrowband Hα filter (panel a), the broadband r-band filter (panel b), and the continuum subtracted Hα-r (panel c). Each panel shows a 4′ × 4′ field of view, with the dashed circle representing the extent of the diffuse X-ray emission from 1RXS 1140818.1+792113 (see Fig. 1). Radio contours from the 6″ LOFAR mosaic are overlaid in panel a.