Overview of Si IV burst spectra (gray) and k-means centroids (colored) that were identified in all observations from 2013 to 2014. Positions of blend lines are drawn as vertical dotted lines. #spec indicates how many spectra are drawn in a given panel for a given binning (“bin”) and #obs indicates in how many of the 287 observations a given type occurred. The yellow-framed burst spectra are analyzed in more detail in Sect. 3.1 and those framed in blue in Sect. 3.2.