TITLE: GCN CIRCULAR NUMBER: 39471 SUBJECT: GRB 250221A: Swift-BAT refined analysis DATE: 25/02/25 14:19:03 GMT FROM: Mike Moss at NASA GSFC mikejmoss3@gmail.com
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Caputo (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), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team):
Using the data set from T-479 to T+600 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250221A (trigger #1290305) (R. Caputo, et al., GCN Circ. 39396). The BAT ground-calculated position is RA, Dec = 59.476, -15.137 deg which is RA(J2000) = 03h 57m 54.4s Dec(J2000) = -15d 08' 11.8" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 19%.
The mask-weighted light curve displays a single short pulse. T90 (15-350 keV) is 1.80 +- 0.32 sec (estimated error including systematics).
The time-averaged spectrum from T-0.22 to T+1.84 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.43 +- 0.23. The fluence in the 15-150 keV band is 3.9 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.42 sec in the 15-150 keV band is 2.9 +- 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/1290305
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