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GCN Circular 12726

Subject

GRB 111225A, Swift-BAT refined analysis

Date

2011-12-25T15:51:38Z (12 years ago)

From

Takanori Sakamoto at NASA/GSFC <takanori.sakamoto-1@nasa.gov>

W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), 
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), 
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), 
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. H. Siegel (PSU) 
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+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 111225A (trigger #510341)
(Siegel, et al., GCN Circ. 12720Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 13.158, 51.573 deg which is 
  RA(J2000)  =  00h 52m 37.9s 
  Dec(J2000) = +51d 34' 21.8" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 93%.

The mask-weighted light curve shows a FRED like structure with the emission 
starting at ~T-15 sec, peaking at ~T-5 sec and ending at ~T+150 sec.  
T90 (15-350 keV) is 106.8 +- 26.7 sec (estimated error including systematics).

The time-averaged spectrum from T-14.28 to T+111.24 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.70 +- 0.15.  The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T-4.40 sec in the 15-150 keV band
is 0.7 +- 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/510341/BA/