TITLE: GCN CIRCULAR NUMBER: 41923 SUBJECT: GRB 250920B: Swift-BAT refined analysis DATE: 25/09/21 02:14:23 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), (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250920B (trigger #1351008) (R. Gupta, et al., GCN Circ. 41898). The BAT ground-calculated position is RA, Dec = 187.316, 47.843 deg which is RA(J2000) = 12h 29m 15.8s Dec(J2000) = +47d 50' 33.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 57%. The BAT mask-weighted light curve shows multiple emission episodes extending over ~150 sec. T90 (15-350 keV) is 128.44 +- 1.00 sec (estimated error including systematics). The time-averaged spectrum from T-4.83 to T+149.43 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.31 +- 0.15, and Epeak of 182.2 +- 153.0 keV (chi squared 36.64 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.1 +- 0.0 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T+0.29 sec in the 15-150 keV band is 5.0 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.52 +- 0.04 (chi squared 42.79 for 57 d.o.f.). 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/1351008 View this GCN Circular online at https://gcn.nasa.gov/circulars/41923. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...