TITLE: GCN CIRCULAR NUMBER: 6397 SUBJECT: GRB 070509, Swift-BAT refined analysis DATE: 07/05/09 13:32:02 GMT FROM: Scott Barthelmy at NASA/GSFC J. Cummings (GSFC/UMBC), L. Barbier (GSFC), S. D. Barthelmy (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), L. Vetere (PSU) on behalf of the Swift-BAT team: Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 070509 (trigger #278903) (Vetere, et al., GCN Circ. PSU). The BAT ground-calculated position is RA, Dec = 237.874, -78.657 deg, which is RA(J2000) = 15h 51m 29.8s Dec(J2000) = -78d 39' 24.0" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 92%. The mask-weighted lightcurve shows a single FRED-like pulse starting at T-2 sec, peaking at T_0, and ending at ~T+10 sec. T90 (15-350 keV) is 7.7 +- 0.3 sec (estimated error including systematics). The time-averaged spectrum from T-1.1 to T+7.9 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.33 +- 0.25. The fluence in the 15-150 keV band is 1.7 +- 0.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.31 sec in the 15-150 keV band is 0.7 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. We note that the initial TDRSS messages for this burst were delayed ~6 min in transmission to the ground because the burst occurred during a Malindi downlink session.