TITLE:   GCN CIRCULAR
NUMBER:  22038
SUBJECT: GRB 171020A: Swift-BAT refined analysis
DATE:    17/10/21 15:54:40 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC), 
J. R. Cummings (CPI), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), K. L. Page (U Leicester)
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-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 171020A (trigger #780845)
(Page et al., GCN Circ. 22028).  The BAT ground-calculated position is
RA, Dec = 39.260, 15.199 deg which is 
  RA(J2000)  =  02h 37m 02.3s 
  Dec(J2000) = +15d 11' 57.0" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.

The mask-weighted light curve shows a weak pulse that starts at ~T0 and 
ends at ~ T+45 s. T90 (15-350 keV) is 41.9 +- 9.2 sec (estimated error 
including systematics).

The time-averaged spectrum from T-0.97 to T+46.68 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.04 +- 0.20.  The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+19.92 sec in the 15-150 keV band
is 0.7 +- 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/780845/BA/