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GCN Circular 14469

Subject
GRB 130427B: Swift-BAT refined analysis
Date
2013-04-27T18:55:42Z (11 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), A. Maselli (INAF-IASFPA),
D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 130427B (trigger #554635)
(Maelli, et al., GCN Circ. 14460).  The BAT ground-calculated position is
RA, Dec = 314.900, -22.548 deg, which is 
   RA(J2000)  =  20h 59m 36.0s 
   Dec(J2000) = -22d 32' 51.6" 
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 22%.
 
The mask-weighted light curve shows shows a very small peak at ~T-3 sec,
the main peak starting at ~T-1 sec, peaking at ~T+2 sec, and ending at
~T+40 sec.  T90 (15-350 keV) is 27.0 +- 7.3 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-1.29 to T+32.71 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.64 +- 0.15.  The fluence in the 15-150 keV band is 1.5 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+0.71 sec in the 15-150 keV band
is 3.0 +- 0.4 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/554635/BA/
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