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Recently, in a study the X-ray flaring activity of Sgr A* with Chandra andXMM-Newton public observations from 1999 to 2014 and 2014 Swift data, it hasbeen argued that the "bright and very bright" flaring rate raised from 2014Aug. 31. Thanks to 482ks of observations performed in 2015 with Chandra,XMM-Newton and Swift, we test the significance of this rise of flaring rate anddetermine the threshold of unabsorbed flare flux or fluence leading to anyflaring-rate change. The mean unabsorbed fluxes of the 107 flares detected inthe 1999-2015 observations are consistently computed from the extracted spectraand calibration files, assuming the same spectral parameters. We construct theobserved flare fluxes and durations distribution for the XMM-Newton and Chandraflares and correct it from the detection biases to estimate the intrinsicdistribution from which we determine the average flare detection efficiency foreach observation. We apply the BB algorithm on the flare arrival timescorrected from the corresponding efficiency. We confirm a constant overallflaring rate in 1999-2015 and a rise in the flaring rate for the mostluminous/energetic flares from 2014 Aug. 31 (4 months after the passage of theDSO/G2 close to Sgr A*). We also identify a decay of the flaring rate for theless luminous and less energetic flares from 2013 Aug. and Nov., respectively(10 and 7 months before the pericenter of the DSO/G2). The decay of the faintflaring rate is difficult to explain by the tidal disruption of the DSO/G2,whose stellar nature is now well established, since it occurred well before itspericenter. Moreover, a mass transfer from the DSO/G2 to Sgr A* is not requiredto produce the rise in the bright flaring rate since the energy saved by thedecay of the number of faint flares during a long time period may be laterreleased by several bright flares during a shorter time period. (abridged)

astronomy and astrophysics

Sixteen years of X-ray monitoring of Sagittarius A*: Evidence for a  decay of the faint flaring rate from 2013 August, 13 months before a rise in  the bright flaring rate