TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4948 SUBJECT: GRB 060403: Refined analysis of the Swift-BAT burst DATE: 06/04/03 21:47:08 GMT FROM: Scott Barthelmy at NASA/GSFC J. Tueller (GSFC), L. Barbier (GSFC), S.D. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), J. Norris (GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS) on behalf of the Swift-BAT team: Using the data set from T-119 to T+183 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060403 (trigger #203755) (Boyd, et al., GCN 4945). The BAT ground-calculated position is RA,Dec = 282.336, 8.328 deg {18h 49m 20.7s, 8d 19' 39.8"} (J2000) +- 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a single FRED-like peak starting at T-8 sec and extending out to about T+32 sec. T90 (15-350 keV) is 30 +- 3 sec (estimated error including systematics). The spectral lags place this burst in the long-burst class (Norris et al. 2005, ApJ, 627, 324): 1.23 +- 0.55 s (15-25 keV vs. 50-100 keV) and 0.80 +- 0.24 s (25-50 keV vs. 50-100 keV). The time-averaged spectrum from T-6.2 to T+32.1 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.08 +- 0.09. The fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T-1.22 sec in the 15-150 keV band is 1.0 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level.