TITLE: GCN CIRCULAR NUMBER: 23264 SUBJECT: GRB 180924A: Swift-BAT refined analysis DATE: 18/09/24 20:32:53 GMT FROM: Scott Barthelmy at NASA/GSFC M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+304 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180924A (trigger #863186) (Ukwata, et al., GCN Circ. 23261). The BAT ground-calculated position is RA, Dec = 49.207, -58.524 deg, which is RA(J2000) = 03h 16m 49.7s Dec(J2000) = -58d 31' 27.6" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a couple peaks starting at ~T-90 sec, peaking at ~T=50 and ~T0 sec, and returning to baseline ~T+30 sec. T90 (15-350 keV) is 95.1 +- 10.9 sec (estimated error including systematics). The time-averaged spectrum from T-85.15 to T+26.35 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.94 +- 0.14. The fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+2.73 sec in the 15-150 keV band is 0.6 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/863186/BA/