TITLE: GCN CIRCULAR NUMBER: 11001 SUBJECT: GRB 100727A, Swift-BAT refined analysis DATE: 10/07/27 14:00:16 GMT FROM: Hans Krimm at NASA-GSFC M. Stamatikos (GSFC/ORAU), 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/UMD), D. C. Morris (GWU/GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+617 sec from the recent telemetry downlink, we report further analysis of BAT GRB 100727A (trigger #430094) (Morris, et al., GCN Circ. 10998). The BAT ground-calculated position is RA, Dec = 154.187, -21.417 deg which is RA(J2000) = 10h 16m 44.8s Dec(J2000) = -21d 25' 02.7" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%. The burst began with weak precursor activity starting at T-80 sec and peaking at T-40 sec. The main pulse, a mostly featureless FRED profile, began at T-2 sec and continued to approximately T+50 sec. T90 (15-350 keV) is 84 +- 14 sec (estimated error including systematics). The time-averaged spectrum from T-82.0 to T+29.8 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.81 +- 0.13. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10-6 erg/cm2. The 1-sec peak photon flux measured from T+1.33 sec in the 15-150 keV band is 1.2 +- 0.1 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/430094/BA/