TITLE: GCN CIRCULAR NUMBER: 41812 SUBJECT: GRB 250911A: Swift-BAT refined analysis DATE: 25/09/12 10:16:27 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov> D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Gupta (GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII), 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-239 to T+200 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250911 A (trigger #1348587) (Klingler, et al., GCN Circ. 41781). The BAT ground-calculated position is RA, Dec = 263.752, -16.841 deg which is RA(J2000) = 17h 35m 00.6s Dec(J2000) = -16d 50' 28.0" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 29%. The mask-weighted BAT light curve shows two emission episodes (a precursor followed by main emission) separated by quiescent gap of ~ 80 sec. T90 (15-350 keV) is 128.42 +- 87.23 sec (estimated error including systematics). The time-averaged spectrum from T-1.35 to T+147.24 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.00 +- 0.20, and Epeak of 170.5 +- 84.5 keV (chi squared 56.83 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.5 +- 0.0 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T+103.94 sec in the 15-150 keV band is 8.6 +- 0.6 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.35 +- 0.05 (chi squared 66.73 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/1348587 View this GCN Circular online at https://gcn.nasa.gov/circulars/41812. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...