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GCN Circular 12551

Subject
GRB 111109A: Swift-BAT refined analysis
Date
2011-11-09T14:14:55Z (13 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
C. Pagani (U Leicester), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+645 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 111109A (trigger #507342)
(Pagani, et al., GCN Circ. 12548).  The BAT ground-calculated position is
RA, Dec = 118.248, -41.588 deg, which is 
   RA(J2000)  =  07h 52m 59.5s 
   Dec(J2000) = -41d 35' 18.3" 
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 91%.
 
The mask-weighted light curve shows a couple overlapping peaks starting
at ~T-5 sec, peaking at ~T+2 sec, and ending at ~T+20 sec.  There is a
hint of possible precursor activity (~2 sigma) at ~T-110 sec.  We note
that the burst location went out of the BAT FoV at ~T+120 sec (a slew
due to an observing constraint).  T90 (15-350 keV) is 13.0 +- 3.2 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-5.60 to T+8.40 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.86 +- 0.26.  The fluence in the 15-150 keV band is 2.4 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+1.40 sec in the 15-150 keV band
is 0.5 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/507342/BA/
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