TITLE:   GCN CIRCULAR
NUMBER:  26495
SUBJECT: GRB 191218A: Swift-BAT refined analysis
DATE:    19/12/19 03:53:53 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), E. Troja (GSFC/UMD),
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 191218A (trigger #944916)
(Troja et al., GCN Circ. 26480).  The BAT ground-calculated position is
RA, Dec = 301.070, -40.277 deg which is
   RA(J2000)  =  20h 04m 16.7s
   Dec(J2000) = -40d 16' 38.8"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 9%.

The mask weighted light curve shows two peaks at ~T+4 s and ~T+45 s. The
overall structure starts at ~T-2 s and lasts till ~T+58 s.
T90 (15-350 keV) is 44.67 +- 0.73 sec (estimated error including systematics).

The time-averaged spectrum from T-0.23 to T+46.03 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.12 +- 0.10.  The fluence in the 15-150 keV band is 7.8 +- 0.4 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.66 sec in the 15-150 keV band
is 6.3 +- 0.9 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/944916/BA/