2,068 research outputs found
The X-ray flaring properties of Sgr A* during six years of monitoring with Swift
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.Comment: 8 pages, 5 figures, 3 tables. Shortened, accepted to Ap
Swift/XRT detects a new accretion outburst from the Galactic center X-ray transient AX J1745.6-2901
Starting on 2021 July 10, our daily Swift/XRT monitoring observations of the Galactic center (Degenaar et al. 2015) detect activity from a transient X-ray source located ~1' to the South-East of Sgr A*. Running the online XRT products tool on the 1.0-ks exposure obtained on July 13 (obsID 00096134085), we determine an 'enhanced' position for this X-ray transient of R.A. = 17:45:35.71, Dec. = -29:01:33.2 (J2000) with a 90% confidence error of 2.8" (Goad et al. 2007; Evans et al. 2009)
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