TITLE: GCN CIRCULAR NUMBER: 17675 SUBJECT: GRB 150403A: Swift-BAT refined analysis DATE: 15/04/04 18:40:14 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150403A (trigger #637044) (Lien, et al., GCN Circ. 17665). The BAT ground-calculated position is RA, Dec = 311.505, -62.706 deg which is RA(J2000) = 20h 46m 01.1s Dec(J2000) = -62d 42' 20.5" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 40%. The mask-weighted light curve shows a single bright peak. The main structure starts at ~ T-10 s, peaks at ~ T+6 s, and ends at ~ T+35 s. There are some weaker emissions that starts at ~ T-170 s and lasts till ~ T+195 s. T90 (15-350 keV) is 40.90 +- 11.72 sec (estimated error including systematics). The time-averaged spectrum from T-83.15 to T+145.37 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.23 +- 0.04. The fluence in the 15-150 keV band is 1.7 +- 0.03 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from T+5.80 sec in the 15-150 keV band is 17.6 +- 0.6 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/637044/BA/