Large Flare from Sgr A* Detected by Swift
ATel #5006; N. Degenaar, M. T. Reynolds, J. M. Miller (Michigan), J. A. Kennea (Penn State), R Wijnands (Amsterdam)
on 25 Apr 2013; 00:54 UT
Credential Certification: Mark Reynolds (email@example.com)
Subjects: Radio, Infra-Red, X-ray, AGN, Black Hole, Transient
Referred to by ATel #: 5009, 5011, 5013, 5014, 5016, 5020, 5025, 5046, 5053, 5070, 5074, 5124, 5159, 5222, 5246, 5254, 5332, 5847, 7023
We report the detection of a large X-ray flare from a position consistent with Sgr A* during regular
monitoring observations of the Galactic center with Swift.
In a 1ks observation on 2013-04-24 (17:34UT) a large flare is detected. Using an 10" radius
extraction region centred on the known radio position, we measure a count rate of 0.11+/-0.1 ct/s.
Comparing to the long term X-ray lightcurve of Sgr A* accumulated by Swift from 2006-2011 (Degenaar
et al., 2013), the flare is consistent with the largest count rate detected from Sgr A* by Swift to
A total of 122 counts are detected during the observation facilitating basic spectral
fitting. Assuming a fixed column density of 9.1e22 cm^-3 (see Degenaar et al. 2013) and fitting with
a power-law in the 2 - 10 keV bandpass, we measure
norm: 0.018 +0.019 -0.01
where the errors are at the 90% confidence level, resulting in an absorbed flux of 2.1e-11 erg/s/cm^2 (2-10 keV), or a luminosity of ~ 1.6e35 erg/s for
an assumed distance of 8 kpc. These properties are consistent with the most luminous X-ray flares
previously observed from Sgr A*, e.g., Degenaar et al. (2013), Nowak et al. (2012), Porquet et
al. (2003, 2008), Baganoff et al. (2001).
Swift is carrying out a daily monitoring campaign throughout 2013 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
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Swift Sgr A* Monitoring Campaign Website