Evolution of the mean X-ray flaring rate from 1999 to 2015 by Chandra (top panel), XMM-Newton (middle panel), and Swift (bottom panel). The vertical gray stripe with the dot-dashed line is the time range of the DSO/G2 pericenter passage (Valencia-S. et al. 2015). The blue and orange lines are the cumulative number of flares and the cumulative observing time, respectively; the black line is the ratio of these values corresponding to the mean flaring rate.