Combination of our 2011 beam pattern with the localization distribution of the DM = 54.7 pc cm⁻³ candidate from Rubio-Herrera et al. (2013) in blue. The overall outline and beam numbers over the 2011 observation are shown; the 25 absent beams failed initial processing. Because observations were taken around transit, the beams are close to circular. The size of the blue ellipses indicates the S/N of the DM = 54.7 pc cm⁻³ single-pulse detection in the WSRT subbeam at that location. In the background we show the H I peak brightness map at 60 arcsec and 6 km s⁻¹ resolution, as observed with WSRT (Braun et al. 2009). The 91 tied-array beams pattern from 2014 is overlaid on a 10 h LOFAR imaging observation of M 31, adopted from M18.