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GCN Circular 26608

Subject
GRB 191227A: Swift-BAT refined analysis
Date
2019-12-28T17:57:54Z (4 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
M. Stamatikos (OSU), 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), A. Melandri (INAF-OAB),
D. M. Palmer (LANL), T. Sakamoto (AGU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-61 to T+242 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 191227A (trigger #946344)
(Melandri et al., GCN Circ. 26595).  The BAT ground-calculated position is
RA, Dec = 319.172, -16.717 deg which is
   RA(J2000)  =  21h 16m 41.4s
   Dec(J2000) = -16d 43' 02.5"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 13%.

The mask-weighted light curve shows many overlapping pulses
that starts from ~T-30 s and ends at ~T+105 s. Several obvious peaks
can be seen at ~T0, ~T+3 s, ~T+5 s, and ~T+11 s, respectively.
T90 (15-350 keV) is 58.5 +- 14.4 sec (estimated error including
systematics).

The time-averaged spectrum from T-30.55 to T+105.93 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.30 +- 0.05.  The fluence in the 15-150 keV band is 2.5 +- 0.1 x 10^-5
erg/cm2.
The 1-sec peak photon flux measured from T+5.28 sec in the 15-150 keV band
is 21.8 +- 1.3 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/946344/BA/
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