X-ray Flare from Galactic Center Detected by Swift
ATel #11313; Mark Reynolds (University of Michigan), Jamie Kennea (Penn State University), Jon Miller (University of Michigan), Nathalie Degenaar (University of Amsterdam), Rudy Wijnands (University of Amsterdam), on behalf of a larger collaboration
on 17 Feb 2018; 05:39 UT
Credential Certification: Mark Reynolds (email@example.com)
Subjects: Radio, Millimeter, Infra-Red, X-ray, Request for Observations, AGN, Black Hole
We report the detection of a large X-ray flare, in a 1ks XRT observation on 2018-02-17 (00:45UT), originating from the direction of the Galactic center during regular monitoring observations with Swift (Degenaar+ 2015, JHEA 7, 137).
The source is observed to be variable (0.02 ct/s -- 0.08 ct/s) with an average count rate of 0.04+/-0.01 ct/s resulting in a total of 40 counts detected during the observation, facilitating basic spectral fitting. Assuming a fixed column density of 9.1e22 cm^-2 (Degenaar+ 2015) and fitting with a power-law in the 2 - 10 keV bandpass, we measure (68% confidence)
Gamma: 1.5 +/- 0.6
norm: 0.003 +0.004 -0.002
resulting in an absorbed flux of ~ 1e-11 erg/s/cm^2 (2-10 keV), or a luminosity of ~ 7.7e34 erg/s for an assumed distance of 8 kpc.
The position of the source of this flare is nominally consistent with the position of Sgr A*. The properties of this flare are consistent with previous detections of flares from Sgr A* as part of the long term Galactic center monitoring program (Degenaar+ 2013, ApJ, 769, 155). Swift will observe the GC region again later today as part of the regular monitoring program (Atel #11263) and significant further evolution will be reported in subsequent telegrams.
Follow-up observations are encouraged to determine the source of this flare.
Our daily Swift X-ray monitoring campaign of the Galactic center will continue throughout 2018. Updates on new observations are immediately posted at the Swift Sgr A* Monitoring Campaign website.