TITLE: GCN CIRCULAR NUMBER: 12383 SUBJECT: GRB 110921A, Swift-BAT refined analysis DATE: 11/09/22 01:08:38 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (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 110921A (trigger #503652) (Baumgartner, et al., GCN Circ. 12373). The BAT ground-calculated position is RA, Dec = 294.094, 36.355 deg which is RA(J2000) = 19h 36m 22.6s Dec(J2000) = +36d 21' 19.8" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 15%. The mask-weighted light curve shows multiple weak peaks. T90 (15-350 keV) was 48.00 +- 22.63 sec (estimated error including systematics). The time-averaged spectrum from T-31.55 to T+16.45 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.57 +- 0.17. The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+7.95 sec in the 15-150 keV band is 0.2 +- 0.4 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/503652/BA/