TITLE: GCN CIRCULAR NUMBER: 12640 SUBJECT: GRB 111209A, Swift-BAT refined analysis DATE: 11/12/09 18:58:12 GMT FROM: Takanori Sakamoto at NASA/GSFC D. M. Palmer (LANL), 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), C. B. Markwardt (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from the recent telemetry downlink, we report further analysis of BAT GRB 111209A (trigger #509336 and #509337) (Hoversten, et al., GCN Circ. 12632). The BAT ground-calculated position using the event data of trigger #509337 (on-axis observation) is RA, Dec = 14.350, -46.799 deg which is RA(J2000) = 00h 57m 24.1s Dec(J2000) = -46d 47' 57.1" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows an excess rate already around T-150 s when the spacecraft settled to the pre-planned target (T is the BAT trigger time of #509336, which is 07:12:08.3 UT). A gradual increase in the rate continues up to T+850s. And then, the rate started to decay. The positive rate is still seen at T+1400 s where the end of the event data. Further analysis using the BAT survey data is on-going to address the duration of this event detected by BAT. The time-averaged spectrum from 358 to 1337 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.48 +- 0.03. The fluence in the 15-150 keV band measured during this time interval is 3.6 +- 0.1 x 10^-05 erg/cm2. The 1-sec peak photon flux measured from T+824 sec in the 15-150 keV band is 0.5 +- 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/509336/BA/ http://gcn.gsfc.nasa.gov/notices_s/509337/BA/