TITLE: GCN CIRCULAR NUMBER: 14052 SUBJECT: GRB 121209A: Swift-BAT refined analysis DATE: 12/12/10 12:40:00 GMT FROM: Scott Barthelmy at NASA/GSFC T. N. Ukwatta (MSU), 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), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC) (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 121209A (trigger #540964) (Maselli, et al., GCN Circ. 14045). The BAT ground-calculated position is RA, Dec = 326.800, -8.232 deg, which is RA(J2000) = 21h 47m 12.0s Dec(J2000) = -08d 13' 55.8" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 60%. The mask-weighted light curve shows multiple peaks starting at ~T-5 sec, max peak at ~T+28 sec, and ending at ~T+80 sec. T90 (15-350 keV) is 42.7 +- 2.0 sec (estimated error including systematics). The time-averaged spectrum from T-2.16 to T+44.28 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.43 +- 0.08. The fluence in the 15-150 keV band is 2.9 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+27.91 sec in the 15-150 keV band is 3.4 +- 0.3 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/540964/BA/