TITLE: GCN CIRCULAR NUMBER: 22380 SUBJECT: GRB 180204A: Swift-BAT refined analysis DATE: 18/02/04 22:02:03 GMT FROM: Amy Lien at GSFC J. R. Cummings (CPI), S. D. Barthelmy (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), J. P. Norris (BSU), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-186 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180204A (trigger #808483) (Page et al., GCN Circ. 22375). The BAT ground-calculated position is RA, Dec = 330.123, 30.852 deg which is RA(J2000) = 22h 00m 29.5s Dec(J2000) = +30d 51' 07.5" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 70%. The mask-weighted light curve shows two distict pulses. The first pulse starts and peaks at ~T0, and ends at ~T+0.2. The second pulse starts at ~T+0.6 s, peaks at ~T+1 s, and ends at ~T+1.3 s. T90 (15-350 keV) is 1.16 +- 0.12 sec (estimated error including systematics). For the first pulse, the lag analysis finds a lag of -0.2 +- 1 ms for the 100-350 keV to 25-100 keV, and 0.2 +- 1.5 ms for the 50-100 keV to 15-25 keV band. The second pulse has a lag of 5.6 +- 3.9 ms for the 100-350 keV to 25-100 keV, and 3.2 +- 6.6 ms for the 50-100 keV to 15-25 keV band. These values are consistent with those of a short GRB. The time-averaged spectrum from T-0.05 to T+1.29 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.09 +- 0.10. The fluence in the 15-150 keV band is 4.8 +- 0.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.05 sec in the 15-150 keV band is 3.6 +- 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/808483/BA/