TITLE: GCN CIRCULAR NUMBER: 13039 SUBJECT: GRB 120311A, Swift-BAT refined analysis DATE: 12/03/11 16:07:19 GMT FROM: Craig Markwardt at NASA/GSFC M. Stamatikos (OSU), 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), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 120311A (trigger #517469) (Markwardt, et al., GCN Circ. 13032). The BAT ground-calculated position is RA, Dec = 273.075, 14.297 deg which is RA(J2000) = 18h 12m 18.1s Dec(J2000) = +14d 17' 49.0" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 71%. The mask-weighted light curve shows a single gradual-rise exponential-decay peak. T90 (15-350 keV) is 3.5 +- 0.8 sec (estimated error including systematics). The time-averaged spectrum from T-1.38 to T+3.22 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.30 +- 0.15. The fluence in the 15-150 keV band is 3.0 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.07 sec in the 15-150 keV band is 3.2 +- 0.2 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/517469/BA/