TITLE: GCN CIRCULAR NUMBER: 15076 SUBJECT: GRB 130806A, Swift-BAT refined analysis DATE: 13/08/06 22:31:21 GMT FROM: Hans Krimm at NASA-GSFC A. Y. Lien (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), B.P. Gompertz (U Leicester), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 130806A (trigger #565562) (Gompertz, et al., GCN Circ. 15071). The BAT ground-calculated position is RA, Dec = 35.907, 67.525 deg which is RA(J2000) = 02h 23m 37.7s Dec(J2000) = +67d 31' 30.5" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 95%. The mask-weighted light curves shows a faint initial 2-sec long peak starting at T-5 sec, followed by the main peak from T-1 to T+2 sec. T90 (15-350 keV) is 6.1 +- 0.5 sec (estimated error including systematics). The time-averaged spectrum from T-4.5 to T+2.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.50 +- 0.22. The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.32 sec in the 15-150 keV band is 1.3 +- 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/565562/BA/ We note that the fluence ratio in a simple power-law fit between the 25-50 keV band and the 50-100 keV band is 1.41. This fluence ratio is larger than 1.32 which can be achieved in the Band function of alpha=-1.0, beta=-2.5, and Epeak=30 keV. Thus, preliminary analysis shows that Epeak of the burst is very likely around or below 30 keV. Therefore the burst can be classified as an X-ray flash (e.g. Sakamoto et al. 2008, ApJ, 679, 570). A fit to a Band model gives nearly the same reduced chi-squared as a simple power=law fit. The Band fit gives Epeak = 18.9 (+3.2, -5.8) and beta = -2.6 ± 0.3. The alpha parameter is not constrained by the fit.