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

Abstract

Recently, in a study the X-ray flaring activity of Sgr A* with Chandra and XMM-Newton public observations from 1999 to 2014 and 2014 Swift data, it has been argued that the "bright and very bright" flaring rate raised from 2014 Aug. 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 and determine the threshold of unabsorbed flare flux or fluence leading to any flaring-rate change. The mean unabsorbed fluxes of the 107 flares detected in the 1999-2015 observations are consistently computed from the extracted spectra and calibration files, assuming the same spectral parameters. We construct the observed flare fluxes and durations distribution for the XMM-Newton and Chandra flares and correct it from the detection biases to estimate the intrinsic distribution from which we determine the average flare detection efficiency for each observation. We apply the BB algorithm on the flare arrival times corrected from the corresponding efficiency. We confirm a constant overall flaring rate in 1999-2015 and a rise in the flaring rate for the most luminous/energetic flares from 2014 Aug. 31 (4 months after the passage of the DSO/G2 close to Sgr A*). We also identify a decay of the flaring rate for the less 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 faint flaring 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 its pericenter. Moreover, a mass transfer from the DSO/G2 to Sgr A* is not required to produce the rise in the bright flaring rate since the energy saved by the decay of the number of faint flares during a long time period may be later released by several bright flares during a shorter time period. (abridged)

Accepted in A&A in 2017 April 23

References in corpus (12)

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Cited by in corpus (16)

• The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project
• Chandra Spectral and Timing Analysis of Sgr A*'s Brightest X-ray Flares
• A Deep Chandra View of A Candidate Parsec-Scale Jet from the Galactic Center Super-massive Black Hole
• Galactic Center IRS13E: Colliding Stellar Winds or an Intermediate Mass Black Hole?
• Simultaneous Monitoring of X-ray and Radio Variability in Sagittarius A*
• No sign of G2's encounter affecting Sgr A*'s X-ray flaring rate from $Chandra$ observations
• A Systematic Chandra study of Sgr A${}^{\star }$: II. X-ray flare statistics
• A Statistical Study of Soft X-ray Flares on Solar-type Stars
• Continuation of the X-ray monitoring of Sgr A*: the increase in bright flaring rate confirmed
• The long-period massive binary HD~54662 revisited
• Effect of matter geometry on low angular momentum black hole accretion in the Kerr metric
• A Spectroscopic Angle on Central Engine Size Scales in Accreting Neutron Stars
• Influence of flow thickness on general relativistic low angular momentum accretion around spinning black holes
• A 149 minute periodicity underlies the X-ray flaring of Sgr A*
• High Energy Emission from the Galactic Center
• Search for long-term variability of HESS J1745-290