TITLE: GCN CIRCULAR NUMBER: 14252 SUBJECT: SGR 1806-20 outburst (trigger 549841), Swift-BAT refined analysis DATE: 13/02/27 14:22:23 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), 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 (AGU), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) A. Y. Lien (NASA/GSFC/ORAU) (i.e. the Swift-BAT team): Using the data set from T-119 to T+183 sec from the recent telemetry downlink, we report further analysis of the outburst from SGR 1806-20 (trigger #549841) (Burrows, et al., GCN Circ. 14251). The BAT ground-calculated position is RA, Dec = 272.158, -20.399 deg which is RA(J2000) = 18h 08m 38.0s Dec(J2000) = -20d 23' 58.1" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a symmetrical peak with a total width of about 100 msec. T90 (15-350 keV) is 0.05 +- 0.01 sec (estimated error including systematics). There is no evidence of additional outbursts in the post 180 sec of the lightcurve at the 0.2 ph/cm2/sec 3-sigma upper limit. Several models are fit over a time-averaged spectrum from T-0.02 to T+0.04 sec. A simple power-law model shows the power law index of 2.43 +- 0.24 (chi squared 49.55 for 57 d.o.f.). The fluence in the 15-150 keV band is 2.1 +- 0.3 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.49 sec in the 15-150 keV band is 0.5 +- 0.1 ph/cm2/sec. A single blackbody fit to the time-averaged spectrum shows the blackbody temperature of 8.24 +- 1.19 keV (chi squared 54.15 for 57 d.o.f.). A thermal bremsstrahlung model fit shows the temperature of 37.64 +- 11.54 keV (chi squared 45.71 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/549841/BA/