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
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