TITLE:   GCN CIRCULAR
NUMBER:  23555
SUBJECT: GRB 181224A: Swift-BAT refined analysis
DATE:    18/12/25 03:17:55 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), A. Melandri (INAF-OAB),
D. M. Palmer (LANL), 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+450 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 181224A (trigger #878911)
(Melandri et al., GCN Circ. 23554).  The BAT ground-calculated position is
RA, Dec = 125.949, 6.194 deg which is
  RA(J2000)  =  08h 23m 47.7s
  Dec(J2000) = +06d 11' 39.9"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 80%.

The mask-weighted light curve shows a single-peaked structure that starts at
~ T-12 s, peaks at ~ T+1 s, one ends at ~ T+4 s. T90 (15-350 keV) is
12.5 +- 4.2 sec (estimated error including systematics).

The time-averaged spectrum from T-12.04 to T+3.30 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.27 +- 0.20.  The fluence in the 15-150 keV band is 4.9 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.48 sec in the 15-150 keV band
is 1.0 +- 0.2 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/878911/BA/