TITLE:   GCN CIRCULAR
NUMBER:  38721
SUBJECT: GRB 241229B: Swift-BAT refined analysis
DATE:    24/12/30 05:50:24 GMT
FROM:    Amy <yarleen@gmail.com>

S. D. Barthelmy (GSFC), D'Ai (INAF-IASFPA), R. Gupta (GSFC), H. A. Krimm
(NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula
(GSFC/UMBC), T. Sakamoto (AGU) (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 241229B (trigger #1277428)
(D'Ai et al., GCN Circ. 38699).  The BAT ground-calculated position is
RA, Dec = 274.140, 74.694 deg which is
   RA(J2000)  =  18h 16m 33.5s
   Dec(J2000) = +74d 41' 39.5"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 39%.

The mask-weighted light curve shows several overlapping pulses that start
at ~T-3 s and end at ~T+3 s. The main peak occurs at ~T+0.5 s, T90 (15-350
keV) is 5.05 +- 0.65 sec (estimated error including systematics).

The time-averaged spectrum from T-2.62 to T+3.38 sec is best fit by a power
law with an exponential cutoff.  This fit gives a photon index 0.93 +-
0.50, and Epeak of 68.3 +- 22.6 keV (chi squared 47.78 for 56 d.o.f.).  For
this model the total fluence in the 15-150 keV band is 7.0 +- 0.6 x 10^-07
erg/cm2 and the 1-sec peak flux measured from T-0.06 sec in the 15-150 keV
band is 4.0 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon
index of 1.70 +- 0.11 (chi squared 55.86 for 57 d.o.f.).  All the quoted
errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1277428