TITLE: GCN CIRCULAR NUMBER: 7373 SUBJECT: GRB 080307, Swift-BAT refined analysis DATE: 08/03/07 18:47:06 GMT FROM: Goro Sato at GSFC G. Sato (GSFC/ISAS), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), S. T. Holland (CRESST/USRA/GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (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 080307 (trigger #305011) (Holland, et al., GCN Circ. 7362, and Palmer, et al., GCN Circ. 7365). The BAT ground-calculated position is RA, Dec = 136.629, 35.151 deg which is RA(J2000) = 9h 6m 31.0s Dec(J2000) = 35d 9' 4" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 81%. The mask-weighted light curve shows an initial FRED-like peak starting at T+0 sec, and ending around T+140 sec. A strong spectral evolution can be seen in the BAT four energy band light curves. T90 (15-350 keV) is 125.9 +- 24.6 sec (estimated error including systematics). The time-averaged spectrum from T+1.7 to T+146.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.78 +- 0.21. The fluence in the 15-150 keV band is 8.7 +- 1.2 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.90 sec in the 15-150 keV band is 0.4 +- 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/305011/BA/ This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria (Ukwatta et al. arXiv:0802.3815): 1) The power law photon index (= 1.78) is less than 2, 2) The 1-s peak photon flux (= 0.4) is less than 1.0 ph/cm2/s, 3) The light curve variance (= 9.4e-06) is less than 0.0001, 4) The T90/Peak_photon_flux (= 350) is greater than 100. Based on a limited sample of bursts, these criteria yield an 85% chance it has a redshift greater than 3.5.