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X-ray Flare from Galactic Center Detected by Swift

ATel #6456; Mark Reynolds, Nathalie Degenaar, Jon Miller (Michigan), Jamie Kennea (Penn State), Rudy Wijnands (Amsterdam) on behalf of a larger collaboration.
on 10 Sep 2014; 07:13 UT
Credential Certification: Mark Reynolds (markrey@umich.edu)

Subjects: Radio, Millimeter, Sub-Millimeter, Infra-Red, X-ray, Gamma Ray, AGN, Black Hole, Soft Gamma-ray Repeater

Referred to by ATel #: 6458

We report the detection of a large X-ray flare originating from the direction of the Galactic center during regular monitoring observations with Swift.

In a 1ks observation on 2014-09-10 (01:02UT) a large X-ray flare is detected. We measure a source position (J2000) of
alpha: 17:45:40.3
delta: -29:00:29.7
with an uncertainty of approximately 2.5".

The source is observed to be mildly variable (0.02 ct/s - 0.2 ct/s) with an average count rate of 0.08+/-0.01 ct/s resulting in a total of 79 counts detected during the observation, facilitating basic spectral fitting. Assuming a fixed column density of 9.1e22 cm^-2 (see Degenaar et al. 2013) and fitting with a power-law in the 2 - 10 keV bandpass, we measure (90% confidence)

Gamma: 1.1+/-0.6
norm: 0.003 +0.005 -0.002

resulting in an absorbed flux of ~ 2.5e-11 erg/s/cm^2 (2-10 keV), or a luminosity of ~ 1.9e35 erg/s for an assumed distance of 8 kpc.

The position of the source of this flare is consistent with both Sgr A* and the magnetar SGR 1745-29. Swift will observe the GC region again later today as part of the regular monitoring program and significant further evolution will be reported in subsequent telegrams and/or on the project website.

Follow-up observations are encouraged to determine the source of this flare.


Swift is carrying out a daily monitoring campaign throughout 2014 to study the evolution of the X-ray properties of Sgr A* as it interacts with the G2 cloud (Gillessen et al., 2012, 2013). All observations are promptly analyzed and the resulting X-ray lightcurve will be made publicly available at the link below. Bright flares (Lx > 1e35 erg/s) will be reported to the community in further telegrams.

If you would like to receive an automated email update of large flares, please email swift.sgra 'at' gmail.com to be added to the mailing list.

Swift Sgr A* Monitoring Campaign Website