TITLE: GCN CIRCULAR NUMBER: 10896 SUBJECT: GRB 100628A: Swift-BAT refined analysis DATE: 10/06/28 16:16:49 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), T. Sakamoto (GSFC/UMBC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), S. Immler (CRESST/GSFC/UMD), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), G. Sato (ISAS), M. Stamatikos (ORAU/GSFC), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+577 sec from the recent telemetry downlink, we report further analysis of BAT GRB 100628A (trigger #426114) (Immler, et al., GCN Circ. 10895). The BAT ground-calculated position is RA, Dec = 225.943, -31.653 deg, which is RA(J2000) = 15h 03m 46.2s Dec(J2000) = -31d 39' 10.2" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 70%. The mask-weighted light curve shows two overlapping peaks starting at ~T_zero to ~T+0.04 sec. T90 (15-350 keV) is 0.036 +- 0.009 sec (estimated error including systematics). The time-averaged spectrum from T-0.004 to T+0.036 sec is equally well fit by the exponential cutof powerlaw and a blackbody: Exponential cutoff: photon index -2.67 +1.8/-3.7, and Epeak of 74.1 +- 11.4 keV (chi squared 60.5 for 56 d.o.f.). Blackbody: kT = 19.8 +- 2.9 (chi squared 61.0 for 57 d.o.f.). The total fluence in the 15-150 keV band is 2.5 +- 0.5 x 10^-8 erg/cm2 and the 1-sec peak flux measured from T-0.48 sec in the 15-150 keV band is 0.5 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.26 +- 0.25 (chi squared 81.3 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/426114/BA/