TITLE: GCN CIRCULAR NUMBER: 14296 SUBJECT: GRB 130313A: Swift-BAT refined analysis DATE: 13/03/13 19:48:15 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), B.P. Gompertz (U Leicester), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-60 to T+180 sec from the recent telemetry downlink, we report further analysis of BAT GRB 130313A (trigger #550906) (Gompertz, et al., GCN Circ. 14293). The BAT ground-calculated position is RA, Dec = 236.438, -0.355 deg, which is RA(J2000) = 15h 45m 45.1s Dec(J2000) = -00d 21' 18.0" with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 82%. The mask-weighted light curve shows a single pulse starting at ~T+0.0, peaking at ~T+0.1 sec, and ending at ~T+0.2 sec. T90 (15-350 keV) is 0.26 +- 0.09 sec (estimated error including systematics). The time-averaged spectrum from T-0.02 to T+0.23 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.37 +- 0.36. The fluence in the 15-150 keV band is 3.1 +- 0.7 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.36 sec in the 15-150 keV band is 0.5 +- 0.1 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/550906/BA/