Burst profiles of the 6.7 GHz methanol emission. The time series of the integrated flux density for 18 distinct velocity intervals are shown. The velocity intervals, given between square brackets at the top left of each panel, are selected in order to visualize the substantial changes in maser intensity and largely correspond to the widths of individual spectral features. The dotted line in each panel marks the 1σ level. The consecutive magenta arrows above the bottom abscissa denote the approximate times of the start, (MJD ~56716), the first peak (MJD ~57310), the dip (MJD ~57400), and the second peak (MJD ~57700) of the burst. The red and blue arrows show the dates of JVLA (see Fig. 7) and VLBI (see Fig. 9) observations, respectively.