TITLE: GCN CIRCULAR NUMBER: 8844 SUBJECT: GRB 090123: Swift-BAT refined analysis DATE: 09/01/23 15:28:59 GMT FROM: Scott Barthelmy at NASA/GSFC T. N. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from recent telemetry downlinks, we report further analysis of BAT GRB 090123 (trigger #340895) (Grupe, et al., GCN Circ. 8842). The BAT ground-calculated position is RA, Dec = 6.794, -23.503 deg, which is RA(J2000) = 00h 27m 10.5s Dec(J2000) = -23d 30' 12.6" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 36%. The mask-weighted light curve shows multiple overlapping peaks starting at ~T-48 sec, with the max peak at ~T+3 sec, and ending at ~T+120 sec. T90 (15-350 keV) is 131 +- 23 sec (estimated error including systematics). The time-averaged spectrum from T-49.6 to T+117.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.74 +- 0.12. The fluence in the 15-150 keV band is 2.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.08 sec in the 15-150 keV band is 1.7 +- 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/340895/BA/