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GCN Circular 18514

GRB 151027B: Swift-BAT refined analysis
2015-10-28T14:29:31Z (9 years ago)
Amy Lien at GSFC <>
T. Sakamoto (AGU), S. D. Barthelmy (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), 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 151027B (trigger #661869)
(Ukwatta, et al., GCN Circ. 18499).  The BAT ground-calculated position is
RA, Dec = 76.188, -6.428 deg which is
  RA(J2000)  =  05h 04m 45.0s
  Dec(J2000) = -06d 25' 40.2"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 17%.

The mask-weighted light curve shows a complex structure with several
overlapping peaks that starts at  ~T0 and ends at ~T+100 s. T90 (15-350 keV)
is 80.00 +- 35.78 sec (estimated error including systematics).

The time-averaged spectrum from T+1.00 to T+97.00 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.83 +- 0.27.  The fluence in the 15-150 keV band is 1.5 +- 0.3 x 10^-6 erg/cm2.
The 1-s peak photon flux is unconstrained due to the weakness of the burst.
All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
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