TITLE: GCN CIRCULAR NUMBER: 39821 SUBJECT: GRB 250321A: Swift-BAT refined analysis DATE: 25/03/21 18:34:55 GMT FROM: Rahul Gupta at NASA GSFC rahul.gupta@nasa.gov
R. Gupta (GSFC), S. D. Barthelmy (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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250321A (trigger #1297508) (Gupta, et al., GCN Circ. 39794). The BAT ground-calculated position is RA, Dec = 295.100, 21.055 deg which is RA(J2000) = 19h 40m 23.9s Dec(J2000) = +21d 03' 16.4" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 24%.
The mask-weighted BAT light curve shows a sharp peak at the trigger time, followed by a rapid decline. T90 (15-350 keV) is 6.21 +- 1.36 sec (estimated error including systematics).
The time-averaged spectrum from T-0.14 to T+7.35 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.61 +- 0.19. The fluence in the 15-150 keV band is 6.7 +- 0.8 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.16 sec in the 15-150 keV band is 3.2 +- 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/1297508
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