TITLE: GCN CIRCULAR NUMBER: 20557 SUBJECT: GRB 170126A, Swift-BAT refined analysis DATE: 17/01/28 05:03:02 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), N. Gehrels (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+200 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170126A (trigger #735188) (Kocevski, et al., GCN Circ. 20530). The BAT ground-calculated position is RA, Dec = 263.623, -64.755 deg which is RA(J2000) = 17h 34m 29.4s Dec(J2000) = -64d 45' 18.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 4%. The mask-weighted light curve shows a single-peaked structure that starts at ~T-1 s, peaks at ~T+1 s, and ends at ~T+11 s. T90 (15-350 keV) is 9.5 +- 1.6 sec (estimated error including systematics). The time-averaged spectrum from T-0.8 to T+10.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.54 +- 0.14. The fluence in the 15-150 keV band is 2.8 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.31 sec in the 15-150 keV band is 7.3 +- 1.1 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/735188/BA/