TITLE: GCN CIRCULAR NUMBER: 8338 SUBJECT: GRB 081007, Swift-BAT refined analysis DATE: 08/10/07 20:01:57 GMT FROM: Wayne Baumgartner at GSFC GRB 081007, Swift-BAT refined analysis C. M. Markwardt (UMD/GSFC), 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), K. McLean (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-120 to T+182 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081007 (trigger #330856) (Baumgartner et al., GCN Circ. 8330). The BAT ground-calculated position is RA, Dec = 339.963, -40.146 deg which is RA(J2000) = 22h 39m 51.1s Dec(J2000) = -40d 08' 44.8" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 28%. The mask-weighted light curve shows a large peak of approximately 9 seconds duration at T+0. This peak is seen mostly below 50 keV; a cutoff-powerlaw model fit yields an Epeak of approximately 12 keV. T90 (15-350 keV) is 10.0 +- 4.5 sec (estimated error including systematics). The time-averaged spectrum from T-6.9 to T+7.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.51 +- 0.20. The fluence in the 15-150 keV band is 7.1 +- 0.8 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.10 sec in the 15-150 keV band is 2.6 +- 0.4 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/330856/BA/ We note that the fluence ratio in a simple power-law fit between the 25-50 keV band and the 50-100 keV band is 1.43. This fluence ratio is larger than 1.32 which can be achieved with a Band function of alpha=-1.0, beta=-2.5, and Epeak=30 keV. Thus, preliminary analysis shows that Epeak of the burst is very likely around or below 30 keV. Therefore the burst can be classified as an X-ray flash (e.g. Sakamoto et al. ApJ, 679, 570).