TITLE: GCN CIRCULAR NUMBER: 29021 SUBJECT: GRB 201209A: Swift-BAT refined analysis DATE: 20/12/09 23:01:54 GMT FROM: Hans Krimm at NSF/NASA-GSFC M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J.D. Gropp (PSU), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 201209A (trigger #1011980) (Gropp, et al., GCN Circ. 29005). The BAT ground-calculated position is RA, Dec = 23.096, -1.762 deg which is RA(J2000) = 01h 32m 23.0s Dec(J2000) = -01d 45' 43.8" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 11%. The mask-weighted light curve shows some early emission starting at ~T-20 sec, and two bright, symmetrical peaks centered at T+0 and T+7 sec. The burst has faded to background by T+30 sec. T90 (15-350 keV) is 48.0 +- 16.0 sec (estimated error including systematics). The time-averaged spectrum from T-31.66 to T+32.34 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.56 +- 0.06. The fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from T+7.84 sec in the 15-150 keV band is 12.2 +- 1.1 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/1011980/BA/