TITLE: GCN CIRCULAR NUMBER: 9434 SUBJECT: GRB 090529: Swift-BAT refined analysis DATE: 09/05/29 20:10:34 GMT FROM: Hans Krimm at NASA-GSFC C. B. Markwardt (GSFC/UMD), 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), 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-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 090529 (trigger #353540) (Sakamoto, et al., GCN Circ. 9430). The BAT ground-calculated position is RA, Dec = 212.446, 24.450 deg which is RA(J2000) = 14h 09m 47.1s Dec(J2000) = +24d 26' 58.5" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 83%. The mask-weighted light curve shows that the burst was in progress when it came into the BAT field of view at ~T-50 sec, following a pre-planned slew. The detectable part of the light curve shows an exponentially falling rate, which some possible superimposed peaks at ~T-45, ~T-25 and ~T-15 sec. The count rate is down to background by T+50 seconds. Given that we did not observe the start of the burst, we can only provide a lower limit to T90: T90 (15-350 keV) is > 100 sec. The time-averaged spectrum from T-49.0 to T+39.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.00 +- 0.3. The fluence in the 15-150 keV band is 6.8 +- 1.7 x 10-7 erg/cm2. The 1-sec peak photon flux measured from T-50.0 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/353540/BA/