TITLE: GCN CIRCULAR NUMBER: 10875 SUBJECT: GRB 100621A: Swift-BAT refined analysis DATE: 10/06/21 13:10:27 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), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), 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 100621A (trigger #425151) (Ukwatta, et al., GCN Circ. 10870). The BAT ground-calculated position is RA, Dec = 315.309, -51.102 deg, which is RA(J2000) = 21h 01m 14.1s Dec(J2000) = -51d 06' 08.8" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 97%. The mask-weighted light curve shows three main overlapping peaks starting at ~T-8 sec, with the main peak at ~T+25 sec, and ending at ~T+220 sec. T90 (15-350 keV) is 63.6 +- 1.7 sec (estimated error including systematics). The time-averaged spectrum from T-6 to T+204 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.90 +- 0.03. The fluence in the 15-150 keV band is 2.1 +- 0.0 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from T+24.46 sec in the 15-150 keV band is 12.8 +- 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/425151/BA/