TITLE: GCN CIRCULAR NUMBER: 6807 SUBJECT: GRB 070920, Swift-BAT refined analysis DATE: 07/09/20 15:29:46 GMT FROM: Scott Barthelmy at NASA/GSFC L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-119 to T+300 sec from recent telemetry downlinks, we report further analysis of BAT GRB 070920 (trigger #291614) (Grupe, et al., GCN Circ. 6805). The BAT ground-calculated position is RA, Dec = 100.968, 72.250 deg which is RA(J2000) = 06h 43m 52.2s Dec(J2000) = 72d 14' 59" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted lightcurve shows a single peak (with structure) starting at ~T-15 sec, broadly peaking at ~T+25 sec, and ending at ~T+140 sec. T90 (15-350 keV) is 56 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T+15.1 to T+75.0 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.69 +- 0.21. The fluence in the 15-150 keV band is 5.1 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+30.45 sec in the 15-150 keV band is 0.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level.