TITLE: GCN CIRCULAR NUMBER: 23175 SUBJECT: GRB 180823A, Swift-BAT refined analysis DATE: 18/08/25 20:56:53 GMT FROM: Hans Krimm at NSF/NASA-GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), B. Sbarufatti (PSU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-43 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180823A (trigger #855434) (Sbarufatti, et al., GCN Circ. 23169). The BAT ground-calculated position is RA, Dec = 210.358, 14.901 deg which is RA(J2000) = 14h 01m 25.9s Dec(J2000) = +14d 54' 03.2" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 92%. The available data starts as the burst is rising, but it appears that it includes the entire burst. The mask-weighted light curve shows a double-peaked structure, starting at ~T-43 seconds, with comparably sized peaks at ~T+5 and ~T+20 sec, and returning to near background by T+70 seconds, with a fainter tail out past T+100 seconds. A spacecraft slew took the burst location out of the BAT field of view around T+450 seconds. T90 (15-350 keV) is 80.3 +- 6.9 sec (estimated error including systematics). The time-averaged spectrum from T-37.5 to T+72.0 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.58 +- 0.05. The fluence in the 15-150 keV band is 7.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+18.33 sec in the 15-150 keV band is 2.3 +- 0.2 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/855434/BA/