A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), P. D'Avanzo (INAF-OAB),
H. A. Krimm (NSF/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), 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+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 171027A (trigger #783479)
(D'Avanzo et al., GCN Circ. 22053). The BAT ground-calculated position is
RA, Dec = 61.683, -2.601 deg which is
RA(J2000) = 04h 06m 43.8s
Dec(J2000) = -02d 36' 02.0"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 91%.
The mask-weighted light curve shows a multi-peaked structure that starts
at ~T-2 s and ends at ~T+150 s. The main peak occurs at ~ T+63 s.
T90 (15-350 keV) is 96.6 +- 4.8 sec (estimated error including systematics).
The time-averaged spectrum from T-2.0 to T+132.0 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 1.25 +- 0.18,
and Epeak of 150.4 +- 95.1 keV (chi squared 33.21 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 7.5 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+62.29 sec in the 15-150 keV band is
3.0 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.53 +- 0.04 (chi squared 40.62 for 57 d.o.f.). All the quoted errors
are at the 90% confidence level.
The results of the batgrbproduct analysis are available at