TITLE: GCN CIRCULAR NUMBER: 23500 SUBJECT: GRB 181203A: Swift-BAT refined analysis DATE: 18/12/04 03:52:49 GMT FROM: Amy Lien at GSFC 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), M. Stamatikos (OSU), E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL) (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 181203A (trigger #874475) (Troja et al., GCN Circ. 23493). The BAT ground-calculated position is RA, Dec = 108.341, -39.783 deg which is RA(J2000) = 07h 13m 21.8s Dec(J2000) = -39d 46' 57.1" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 83%. The mask-weighted light curve shows a single-peaked structure that starts at ~T-2 s, peaks at ~T+1 s, and ends at ~T+16 s. T90 (15-350 keV) is 15.30 +- 1.75 sec (estimated error including systematics). The time-averaged spectrum from T-1.96 to T+15.77 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.79 +- 0.15. The fluence in the 15-150 keV band is 7.8 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.02 sec in the 15-150 keV band is 1.1 +- 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/874475/BA/