TITLE: GCN CIRCULAR NUMBER: 8222 SUBJECT: GRB 080913, Swift-BAT refined analysis DATE: 08/09/13 16:07:01 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), P. Schady (MSSL-UCL), J. Tueller (GSFC), T. Ukwatta (GWU) (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 080913 (trigger #324561) (Schady, et al., GCN Circ. 8217). The BAT ground-calculated position is RA, Dec = 65.741, -25.127 deg which is RA(J2000) = 04h 22m 57.9s Dec(J2000) = -25d 07' 38.6" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 39%. The mask-weighted light curve shows multiple overlapping peaks, somewhat smooth in character. T90 (15-350 keV) is 8 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T-3.8 to T+5.2 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.46 +- 0.70, and Epeak of 93.1 +- 56.1 keV (chi squared 38.53 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.6 +- 0.6 x 10-07 erg/cm2 and the 1-sec peak flux measured from T+0.11 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.36 +- 0.15 (chi squared 44.56 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/324561/BA/