TITLE: GCN CIRCULAR NUMBER: 41924 SUBJECT: GRB 250920C: Swift-BAT refined analysis DATE: 25/09/21 02:16:24 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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250920C (trigger #1351039) (R. Gupta, et al., GCN Circ. 41904). The BAT ground-calculated position is RA, Dec = 51.465, -29.646 deg which is RA(J2000) = 03h 25m 51.6s Dec(J2000) = -29d 38' 46.7" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 15%. The BAT mask-weighted light curve exhibits a bright initial peak followed by multiple structured emission episodes, lasting for about 40 sec from the trigger time. T90 (15-350 keV) is 38.02 +- 1.27 sec (estimated error including systematics). The time-averaged spectrum from T-0.44 to T+40.49 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.09 +- 0.18, and Epeak of 133.4 +- 43.9 keV (chi squared 45.87 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.3 +- 0.0 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T-0.12 sec in the 15-150 keV band is 16.9 +- 1.0 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.48 +- 0.04 (chi squared 60.21 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/1351039 View this GCN Circular online at https://gcn.nasa.gov/circulars/41924. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...