TITLE: GCN CIRCULAR NUMBER: 28458 SUBJECT: GRB 200919A: Swift-BAT refined analysis DATE: 20/09/19 17:27:57 GMT FROM: Amy Lien at GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU), 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 200919A (trigger #996503) (Ukwatta et al., GCN Circ. 28454). The BAT ground-calculated position is RA, Dec = 168.899, 32.456 deg which is RA(J2000) = 11h 15m 35.7s Dec(J2000) = +32d 27' 21.8" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 62%. The mask-weighted light curve shows several overlapping pulses that start at ~T-60 s and end at ~T+25 s. The main peak occurs at ~T+5 s. T90 (15-350 keV) is 76.0 +- 6.9 sec (estimated error including systematics). The time-averaged spectrum from T-61.47 to T+24.54 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.13 +- 0.14. The fluence in the 15-150 keV band is 1.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+4.30 sec in the 15-150 keV band is 1.2 +- 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/996503/BA/