TITLE:   GCN CIRCULAR
NUMBER:  39668
SUBJECT: GRB 250225B: Swift-BAT refined analysis
DATE:    25/03/11 18:05:56 GMT
FROM:    Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
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), M. A. Williams (PSU)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+160 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250225B (trigger #1291459)
(Williams et al., GCN Circ. 39473).  The BAT ground-calculated position is
RA, Dec = 306.134, -41.481 deg which is
   RA(J2000)  =  20h 24m 32.2s
   Dec(J2000) = -41d 28' 50.8"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 47%.

The mask-weighted BAT light curve shows a bright peak around the trigger time, followed by multiple fainter peaks. After approximately 160 seconds, the GRB was no longer in the BAT field of view (FOV).
T90 (15-350 keV) is 110.46 +- 2.12 sec (estimated error including systematics).

The time-averaged spectrum from T-0.02 to T+122.46 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.60 +- 0.07.  The fluence in the 15-150 keV band is 6.5 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+1.31 sec in the 15-150 keV band
is 10.4 +- 0.5 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/1291459