TITLE: GCN CIRCULAR NUMBER: 9551 SUBJECT: GRB 090621B: Swift-BAT refined analysis DATE: 09/06/22 13:08:54 GMT FROM: Scott Barthelmy at NASA/GSFC H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), P.A. Curran (MSSL-UCL), E. E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (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 short hard burst GRB 090621B (trigger #355359) (Curran, et al., GCN Circ. 9545). The BAT ground-calculated position is RA, Dec = 313.455, 69.034 deg, which is RA(J2000) = 20h 53m 49.3s Dec(J2000) = +69d 02' 02.9" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 69%. The mask-weighted light curve shows a single peak starting a ~T+0 sec and ending at ~T+0.2 sec. There is a 2.5-sigma hint of extended emission from ~T+150 to ~T+240 sec. T90 (15-350 keV) is 0.14 +- 0.04 sec (estimated error including systematics). The time-averaged spectrum from T-0.028 to T+0.148 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.82 +- 0.23. The fluence in the 15-150 keV band is 7.0 +- 1.0 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band is 3.9 +- 0.5 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/355359/BA/