[vsnet-grb-info 19891] GRB 171004A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21973
SUBJECT: GRB 171004A: Swift-BAT refined analysis
DATE:    17/10/04 21:13:14 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), 
S. B. Cenko (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU)
(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 171004A (trigger #776347)
(Cenko et al., GCN Circ. 21966).  The BAT ground-calculated position is
RA, Dec = 139.150, 52.684 deg which is 
   RA(J2000)  =  09h 16m 35.9s 
   Dec(J2000) = +52d 41' 01.5" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 42%.
 
The mask-weighted light curve shows several overlapping peaks that starts
at ~ T+9 and ends at ~ T+160 s. The burst location went out of the BAT FOV
at ~ T+580 s, and thus we only have information of the burst emission before
then. T90 (15-350 keV) is 107.1 +- 14.5 sec (estimated error including 
systematics).
 
The time-averaged spectrum from T+9.08 to T+138.31 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.67 +- 0.12. The fluence in the 15-150 keV band is 3.0 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+48.34 sec in the 15-150 keV band
is 0.9 +- 0.3 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/776347/BA/