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GCN Circular 12628

Subject
GRB 111208A found in ground analysis of BAT data
Date
2011-12-08T16:35:58Z (12 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori@milkyway.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), C. Graziani (U of Chicago), J. R. Cummings (GSFC/UMBC), 
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), 
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), 
D. M. Palmer (LANL), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), 
T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):

Automated BAT ground analysis found a burst that occurred at 08:28:11 UT 
with a significance of 10.1 sigma (15-200 keV) from the failed event data 
of trigger #509285.  The event is temporally coincident with the Fermi GBM 
345025692.  The best BAT location is RA, Dec = 290.2151, +40.6686 deg, which is

  RA(J2000)  =  19h 20m 51.6s 
  Dec(J2000) = +40d 40' 07.0" 

with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 10%.

The mask-weighted light curve created from the failed event data 
(available from 08:28:12 to 08:28:22 UT) shows a constant positive 
rate from the beginning of the data and then decaying at 08:28:20 UT.  
From the BAT raw light curve, the duration of the event is ~20 sec long.  

The spectrum extracted using the full event data is best fit by a simple 
power-law model.  The power law index of the spectrum is 1.5 +- 0.3.  The 
fluence in 15-150 keV band measured from the 10 sec long event data is 
9.8 +- 1.8 x 10^-7 erg/cm2.  The 1-sec peak photon flux measured from 
08:28:19 UT is 1.3 +- 0.7 ph/cm2/sec.  All the quoted errors are at the 
90% confidence level.  

Swift ToO observation of this burst has been scheduled.
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