TITLE: GCN CIRCULAR NUMBER: 6173 SUBJECT: GRB 070306, Swift-BAT refined analysis DATE: 07/03/06 23:50:38 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), S. B. Pandey (UCL-MSSL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-240 to T+962 sec from recent telemetry downlinks, we report further analysis of BAT GRB 070306 (trigger #263361) (Pandy, et al., GCN Circ. 6169). The BAT ground-calculated position is RA, Dec = 148.097, +10.477 deg which is RA(J2000) = 09h 52m 23.3s Dec(J2000) = 10d 28' 37.2" with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 28%. The mask-weighted lightcurve shows a small precursor peak starting at T-120 through T-105 sec. Then a second pulse (of equal amplitude) starting at ~T-15 sec and exponentially decaying back to background at ~T+50 sec. Then a much larger peak starting at ~T+75 sec, exponentially rising to a peak at T+98 sec, end then exponentially decaying to background at ~T+220 sec. T90 (15-350 keV) is 210 +- 10 sec (estimated error including systematics). The time-averaged spectrum from T-118.8 to T+186.5 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.10. The fluence in the 15-150 keV band is 5.5 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+98.27 sec in the 15-150 keV band is 4.2 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.