TITLE:   GCN CIRCULAR
NUMBER:  39147
SUBJECT: GRB 250129A: Swift-BAT refined analysis
DATE:    25/02/04 20:36:28 GMT
FROM:    Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), 
A. P. Beardmore (U Leicester), R. Gupta (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC), 
A. Y. Lien (U Tampa), 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-571 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250129A (trigger #1285812)
(Beardmore, et al., GCN Circ. 39066).  The BAT ground-calculated position is
RA, Dec = 198.708, 5.029 deg which is 
   RA(J2000)  =  13h 14m 49.8s 
   Dec(J2000) = +05d 01' 44.9" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 84%.
 
The mask-weighted BAT light curve exhibits a multi-peaked and complex structure, with the most prominent peak occurring at approximately T0 + 184 seconds. T90 (15-350 keV) is 262.25 +- 23.71 sec (estimated error including systematics).
 
The time-averaged spectrum from T-64.39 to T+302.62 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.17 +- 0.09.  The fluence in the 15-150 keV band is 5.0 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+184.12 sec in the 15-150 keV band
is 1.4 +- 0.2 ph/cm2/sec.  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/1285812