The X-ray flaring properties of Sgr A* during six years of monitoring with Swift

Abstract

Starting in 2006, Swift has been targeting a region of ~21'X21' around Sagittarius A* (Sgr A*) with the onboard X-ray telescope. The short, quasi-daily observations offer an unique view of the long-term X-ray behavior of the supermassive black hole. We report on the data obtained between 2006 February and 2011 October, which encompasses 715 observations with a total accumulated exposure time of ~0.8 Ms. A total of six X-ray flares were detected with Swift, which all had an average 2-10 keV luminosity of Lx (1-4)E35 erg/s (assuming a distance of 8 kpc). This more than doubles the number of such bright X-ray flares observed from Sgr A*. One of the Swift-detected flares may have been softer than the other five, which would indicate that flares of similar intensity can have different spectral properties. The Swift campaign allows us to constrain the occurrence rate of bright (Lx > 1E35 erg/s) X-ray flares to be ~0.1-0.2 per day, which is in line with previous estimates. This analysis of the occurrence rate and properties of the X-ray flares seen with Swift offers an important calibration point to asses whether the flaring behavior of Sgr A* changes as a result of its interaction with the gas cloud that is projected to make a close passage in 2013.

8 pages, 5 figures, 3 tables. Shortened, accepted to ApJ

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• New observations of the gas cloud G2 in the Galactic Center
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• Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*
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• No sign of G2's encounter affecting Sgr A*'s X-ray flaring rate from $Chandra$ observations
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• Radiative shock oscillation model for the long-term flares of Sgr A*
• Sgr B2 hard X-ray emission with INTEGRAL after 2009: still detectable?
• A Swift study of long-term changes in the X-ray flaring properties of Sagittarius A*
• Physics of Pair Producing Gaps in Black Hole Magnetospheres: Two Dimensional General Relativistic Particle-in-cell Simulations
• Effects of resistivity on standing shocks in low angular momentum flows around black holes
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