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GCN Circular 33115

Subject
GRB 221226B Swift-BAT refined analysis
Date
2022-12-27T22:22:55Z (a year ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC),
H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU),
M. Stamatikos (OSU) (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 221226B (trigger #1145959)
(Cenko, et al., GCN Circ. 33108).  The BAT ground-calculated position is
RA, Dec = 22.903, -41.515 deg which is
  RA(J2000)  =  01h 31m 36.7s
   Dec(J2000) = -41d 30' 52.5"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 97%.

The mask-weighted light curve shows a pulse of approximately 4 seconds
total duration and some substructure.   T90 (15-350 keV) is 3.44 +- 0.57 sec
(estimated error including systematics).

The time-averaged spectrum from T+0.22 to T+4.28 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.16 +- 0.13.  The fluence in the 15-150 keV band is 5.4 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.24 sec in the 15-150 keV band
is 2.6 +- 0.3 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/1145959/BA/
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