TITLE: GCN CIRCULAR NUMBER: 23377 SUBJECT: GRB 181023A: Swift-BAT refined analysis DATE: 18/10/24 01:39:15 GMT FROM: Amy Lien at GSFC T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 181023A (trigger #868427) (Marshall et al., GCN Circ. 23366). The BAT ground-calculated position is RA, Dec = 248.322, 19.581 deg which is RA(J2000) = 16h 33m 17.4s Dec(J2000) = +19d 34' 51.2" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 53%. The mask-weighted light curve shows a complex structure with some weak overlapping pulses that starts at ~T-30 s and ends at ~T+40 s. Note that the burst entered the BAT FOV at T-48 s, and hence there might be additional emission beforehand. T90 (15-350 keV) is 58.0 +- 8.8 sec (estimated error including systematics). The time-averaged spectrum from T-27.62 to T+36.68 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.74 +- 0.24. The fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+32.18 sec in the 15-150 keV band is 1.0 +- 0.3 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/868427/BA/