X-ray Flare from Galactic Center Detected by Swift

ATel #16134; Mark Reynolds (Ohio State University/University of Michigan), Nathalie Degenaar (University of Amsterdam), Rudy Wijnands (University of Amsterdam), Jon Miller (University of Michigan), Jamie Kennea (Penn State University) on behalf of a larger collaboration.
on 16 Jul 2023; 02:15 UT
Credential Certification: Mark Reynolds (markrey@umich.edu)

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We report the detection of an X-ray flare during regular monitoring observations of the Galactic center with the Neil Gehrels Swift Observatory (Degenaar+ 2015, JHEA 7, 137). In a 0.77 ks XRT observation on 2023-07-14 (10:412UT), a flare is detected originating from the direction of Sgr A*.

The source is observed with a net count rate of 0.068+/-0.009 ct/s resulting in a total of 54 counts detected during the observation. Assuming a fixed column density of 16.6e22 cm^-2 (Wang+ 2013, Sci, 341, 981) and fitting with a power-law in the 2 - 10 keV bandpass, we measure (68% confidence)

Gamma: 3.26 +/- 0.53
norm: 0.15 +0.18 -0.08

resulting in an absorbed flux of ~ 1.5e-11 erg/s/cm^2 (2-10 keV), or a luminosity of ~ 1.1e35 erg/s for an assumed distance of 8 kpc. A subsequent observation ~ 67 ks later shows the flux from this region to have returned to background levels.

The position of the source of this flare is nominally consistent with the position of Sgr A*. Swift monitoring of the GC region continues and significant further evolution will be reported in subsequent telegrams.

Our daily Swift X-ray monitoring campaign of the Galactic center will continue throughout 2023. Updates on new observations are immediately posted at the Swift Sgr A* monitoring campaign website (http://swift-sgra.com/).