TITLE: GCN CIRCULAR NUMBER: 18580 SUBJECT: GRB 151111A: Swift-BAT refined analysis DATE: 15/11/11 14:23:50 GMT FROM: Hans Krimm at NASA-GSFC J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), L. M. McCauley (PSU), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), 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 151111A (trigger #663074) (McCauley, et al., GCN Circ. 18578). The BAT ground-calculated position is RA, Dec = 56.850, -44.154 deg which is RA(J2000) = 03h 47m 24.0s Dec(J2000) = -44d 09' 12.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 80%. The mask-weighted light curve shows a single long FRED-shaped peak beginning at T-5 sec, peaking at T+0 sec and fading to background by T+140 sec. T90 (15-350 keV) is 76.93 +- 12.59 sec (estimated error including systematics). The time-averaged spectrum from T-5.62 to T+91.35 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.79 +- 0.45, and Epeak of 56.6 +- 9.2 keV (chi squared 98.19 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.7 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+0.52 sec in the 15-150 keV band is 1.0 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.76 +- 0.00 (chi squared 115.24 for 57 d.o.f.). 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/663074/BA/