TITLE:   GCN CIRCULAR
NUMBER:  19995
SUBJECT: GRB 161004B: Swift-BAT refined analysis
DATE:    16/10/05 13:02:02 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
A. D'Ai (INAF-IASFPA), 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-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 161004B (trigger #715246)
(D'Ai, et al., GCN Circ. 19987).  The BAT ground-calculated position is
RA, Dec = 112.156, -39.896 deg which is
    RA(J2000)  =  07h 28m 37.4s
    Dec(J2000) = -39d 53' 47.3"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.

The mask-weighted light curve shows two overlapping peaks starting at T-10 sec,
peaking at T+1 sec and ending at T+40 sec.  T90 (15-350 keV) is
15.9 +- 0.7 sec (estimated error including systematics).

The time-averaged spectrum from T-5.16 to T+27.31 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.21 +- 0.13,
and Epeak of 177 +- 73 keV (chi squared 35.21 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 8.8 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.36 sec in the 15-150 keV band is
10.1 +- 0.4 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.47 +- 0.03 (chi squared 47.75 for 57 d.o.f.).  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/715246/BA/