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GCN Circular 19505

Subject
Trigger 689353 (possible transient near Sgr A*), Swift-BAT refined analysis
Date
2016-06-07T21:27:11Z (8 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT trigger #689353 (possible transient near Sgr A*;
Barthelmy, et al., GCN Circ. 19499).  The BAT ground-calculated position is
RA, Dec = 266.507, -29.063 deg which is
  RA(J2000)  =  17h 46m 01.6s
  Dec(J2000) = -29d 03' 47.3"
with an uncertainty of 3.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 93%.

The mask-weighted light curve shows some very weak emissions that starts
before the source came into the BAT field of view, and extends beyond the end
of the event data range. The Bayesian-block analysis failed to find the duration
due to the lack of obvious light curve structure.

The time-averaged spectrum from T+0.0 to T+344.0 sec (the BAT image-trigger
interval) is best fit by a simple power-law model.  The power law index of the
time-averaged spectrum is 2.00 +- 0.50.  The fluence in the 15-150 keV band
is 6.4 +- 2.0 x 10^-7 erg/cm2. All the quoted errors are at the 90% confidence
level.

Because of the low-significance detection (5.2 sigma), we cannot rule out the
possibility of this detection is due to instrumental noise.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/689353/BA/
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