[vsnet-grb-info 19641] Swift J181723.1-164300: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21385
SUBJECT: Swift J181723.1-164300: Swift-BAT refined analysis
DATE:    17/07/29 20:08:51 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

S. D. Barthelmy (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),
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 Swift J181723.1-164300 (trigger #765081)
(Barthelmy et al., GCN Circ. 21369).  The BAT ground-calculated position is
RA, Dec = 274.360, -16.721 deg which is
  RA(J2000)  =  18h 17m 26.5s
  Dec(J2000) = -16d 43' 16.5"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 88%.

The mask-weighted light curve shows a single pulse that starts at ~T-5 s,
peaks at ~T0, and ends at ~T+5 s. T90 (15-350 keV) is 9.34 +- 1.07 sec
(estimated error including systematics).

The spectral fit of the time-averaged spectrum from T-4.44 to T+5.45 sec
using a simple power-law model gives a power law index of 4.70 +- 0.74.
The fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.82 sec in the 15-150 keV band
is 0.6 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The power-law index is much softer than any BAT-detected GRBs
(Lien & Sakamoto et al. 2016), we thus conclude that this is a Galactic source
and not a GRB.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/765081/BA/