TITLE: GCN CIRCULAR NUMBER: 41494 SUBJECT: GRB 250821A: Swift-BAT refined analysis DATE: 25/08/22 14:31:30 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov> A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), S. Dichiara (PSU), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), 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-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250821A (trigger #1344131) (Dichiara, et al., GCN Circ. 41462). The BAT ground-calculated position is RA, Dec = 358.427, -28.631 deg which is RA(J2000) = 23h 53m 42.6s Dec(J2000) = -28d 37' 53.3" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 64%. The mask-weighted BAT light curve exhibits a short-duration main emission starting from ~T-0.5 to ~T+1.2 sec, followed by a weaker, extended emission which last up to ~ T+18 sec. T90 (15-350 keV) is 1.52 +- 0.37 sec (estimated error including systematics). The time-averaged spectrum from T-0.46 to T+1.20 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.83 +- 0.41. The fluence in the 15-150 keV band is 1.3 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band is 0.9 +- 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/1344131 View this GCN Circular online at https://gcn.nasa.gov/circulars/41494. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...