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GCN Circular 26535

Subject
GRB 191220A: Swift-BAT refined analysis
Date
2019-12-21T21:19:35Z (4 years ago)
From
Sibasish Laha at GSFC <sibasish.laha@nasa.gov>
D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 191220A (trigger #945344)
(Laha et al., GCN Circ. 26516).  The BAT ground-calculated position is
RA, Dec = 281.335, 26.679 deg which is
   RA(J2000)  =  18h 45m 20.3s
   Dec(J2000) = +26d 40' 43.1"
with an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 19%.


The mask weighted light curve shows complex structures with a duration of ~50 sec, with a hint of some weak emission lasting till ~ T+ 240 s.
The overall structure starts at ~ T-2 sec and lasts till ~ T+60 sec.
T90 (15-350 keV) is 175.55 +- 125.93 sec (estimated error including systematics).

The time-averaged spectrum from T-2.46 to T+248.42 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.12 +- 0.40.  The fluence in the 15-150 keV band is 1.1 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+6.69 sec in the 15-150 keV band
is 1.1 +- 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/945344/BA/
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