TITLE: GCN CIRCULAR NUMBER: 18086 SUBJECT: GRB 150727A: Swift-BAT refined analysis DATE: 15/07/28 12:05:52 GMT FROM: Scott Barthelmy at NASA/GSFC M. Stamatikos (OSU), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), 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), T. Sakamoto (AGU), 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 downlinks, we report further analysis of BAT GRB 150727A (trigger #650530) (Cenko, et al., GCN Circ. 18076). The BAT ground-calculated position is RA, Dec = 203.968, -18.320 deg, which is RA(J2000) = 13h 35m 52.3s Dec(J2000) = -18d 19' 11.4" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 68%. The mask-weighted light curve shows a FRED-like peak starting at ~T-8 sec, peaking at ~T+5 sec, and ramping down to a flat level at ~T+80 sec. There is a second, small peak at ~T+90 sec. The low level emission continues (with a weak decline) out to T+870 sec when observations stop due to an observing constraint. T90 (15-350 keV) is 88 +- 13 sec (estimated error including systematics). The time-averaged spectrum from T-8.70 to T+95.94 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.14 +- 0.07. The fluence in the 15-150 keV band is 3.7 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+9.21 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. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/650530/BA/ [GCN OPS NOTE(29jul15): Per author's request, the typo on the uncertainty in the T90 value was changed from 133 to 13 sec.]