TITLE: GCN CIRCULAR NUMBER: 20001 SUBJECT: GRB 161004A: Swift-BAT refined analysis DATE: 16/10/06 09:03:15 GMT FROM: Takanori Sakamoto at AGU D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), J. P. Norris (BSU), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (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 161004A (trigger #715084) (Evans, et al., GCN Circ. 19979). The BAT ground-calculated position is RA, Dec = 263.127, -0.947 deg which is RA(J2000) = 17h 32m 30.6s Dec(J2000) = -00d 56' 50.7" with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 92%. The mask-weighted light curve shows a single peak starting at T-0.1 sec, peaking at T+0.5 sec and ending at T+5 sec. T90 (15-350 keV) is 1.08 +- 0.21 sec (estimated error including systematics). The time-averaged spectrum from T-0.11 to T+1.06 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.26 +- 0.33. The fluence in the 15-150 keV band is 9.5 +- 1.6 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. Due to a low signal-to-noise of the data, the lag analysis is not possible. Therefore, it is not clear whether this burst belongs to a short GRB or not. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/715084/BA/