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We present a study of the X-ray flaring activity of Sgr A* during all the 150XMM-Newton and Chandra observations pointed at the Milky Way center over thelast 15 years. This includes the latest XMM-Newton and Chandra campaignsdevoted to monitoring the closest approach of the very red Br-Gamma emittingobject called G2. The entire dataset analysed extends from September 1999through November 2014. We employed a Bayesian block analysis to investigate anypossible variations in the characteristics (frequency, energetics, peakintensity, duration) of the flaring events that Sgr A* has exhibited sincetheir discovery in 2001. We observe that the total bright-or-very bright flareluminosity of Sgr A* increased between 2013-2014 by a factor of 2-3 (~3.5 sigmasignificance). We also observe an increase (~99.9% significance) from0.27+-0.04 to 2.5+-1.0 day^-1 of the bright-or-very bright flaring rate of SgrA*, starting in late summer 2014, which happens to be about six months afterG2's peri-center passage. This might indicate that clustering is a generalproperty of bright flares and that it is associated with a stationary noiseprocess producing flares not uniformly distributed in time (similar to what isobserved in other quiescent black holes). If so, the variation in flaringproperties would be revealed only now because of the increased monitoringfrequency. Alternatively, this may be the first sign of an excess accretionactivity induced by the close passage of G2. More observations are necessary todistinguish between these two hypotheses.

Fifteen years of XMM-Newton and Chandra monitoring of Sgr A*: Evidence for a recent increase in the bright flaring rate