TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5064 SUBJECT: GRB 060502B: Refined analysis of the Swift-BAT short burst DATE: 06/05/03 04:31:23 GMT FROM: Scott Barthelmy at NASA/GSFC G. Sato (ISAS), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), M. Koss (UMD), C. Markwardt (GSFC/UMD), J. Norris (GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU), E. Troja (INAF-IASFPA), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-119 to T+183 sec from the recent telemetry downlink, we report further analysis of BAT GRB 060502B (trigger #208275) (Troja, et al., GCN 5055). The BAT ground-calculated position is RA,Dec = 278.949, 52.642 deg {18h 35m 47.7s, 52d 38' 32.5"} (J2000) +- 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 92%. The lightcurve consists of two spikes. The main peak starts at ~T-0.060 and has a FWHM of ~40 msec. Its rise is faster than the decay. There is also a possible second peak (a precurrsor) starting at T-0.3 sec with a FWHM of ~100 msec and a significance of only ~4 sigma. T90 (15-350 keV) is 90 +- 20 msec (estimated error including systematics). The lag analysis shows this burst to be cleanly in the short hard burst class (Norris and Bonnell, 2006, ApJ, accepted; see, Figure 3). Specifically, the measured lags for the main peak are: -4.0 ms +- 3.0 ms (15-25 keV vs. 50-100 keV) -0.2 ms +- 2.8 ms (25-50 keV vs. 100-350 keV) The time-averaged spectrum from T-0.05 to T+0.04 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.92 +- 0.23. The fluence in the 15-150 keV band is 4 +- 0.5 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.43 sec in the 15-150 keV band is 4.4 +- 0.6 ph/cm2/sec. All the quoted errors are at the 90% confidence level.