TITLE: GCN CIRCULAR NUMBER: 13828 SUBJECT: GRB 120927A, Swift-BAT refined analysis DATE: 12/09/28 17:04:37 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift GRB 120927A, Swift-BAT refined analysis D. M. Palmer (LANL), 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), A. Maselli (INAF-IASFPA), 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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 120927A (trigger #534815) (Maselli, et al., GCN Circ. 13822). The BAT ground-calculated position is RA, Dec = 136.606, 0.420 deg which is RA(J2000) = 09h 06m 25.3s Dec(J2000) = +00d 25' 13.5" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 64%. The mask-weighted light curve shows multiple overlapping peaks with an overall FRED profile starting about T-15 seconds and significant until about T+32 seconds. T90 (15-350 keV) is 43 +- 18 sec (estimated error including systematics). The time-averaged spectrum from T-37.94 to T+41.04 sec is best fit by a power lawwith an exponential cutoff. This fit gives a photon index 0.63 +- 0.38, and Epeak of 66.1 +- 9.6 keV (chi squared 50.98 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.6 +- 0.3 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T-3.93 sec in the 15-150 keV band is 1.6 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.64 +- 0.08 (chi squared 77.30 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/534815/BA/