TITLE: GCN CIRCULAR NUMBER: 23653 SUBJECT: GRB 190109A: Swift-BAT refined analysis DATE: 19/01/09 15:23:32 GMT FROM: Scott Barthelmy at NASA/GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J. D. Gropp (PSU), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (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 190109A (trigger #882747) (Gropp, et al., GCN Circ. 23642). The BAT ground-calculated position is RA, Dec = 33.213, 38.111 deg, which is RA(J2000) = 02h 12m 51.2s Dec(J2000) = +38d 06' 39.5" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 28%. The mask-weighted light curve shows several overlapping peaks starting at ~T+1 sec, peaking at ~T+40 sec, and returning to baseline at ~T+200 sec. T90 (15-350 keV) is 115.0 +- 33.5 sec (estimated error including systematics). The time-averaged spectrum from T+5.86 to T+205.36 sec (with a 1.03 sec gap in the data at T+111.97 sec) is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.36 +- 0.47, and Epeak of 49.7 +- 4.0 keV (chi squared 46.05 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.5 +- 0.3 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+38.82 sec in the 15-150 keV band is 1.9 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.86 +- 0.08 (chi squared 87.76 for 57 d.o.f.). 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/882747/BA/