[vsnet-grb-info 19656] Swift J181723.1-164300: Swift detection of another pulse of the new Galactic source

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21400
SUBJECT: Swift J181723.1-164300: Swift detection of another pulse of the new Galactic source
DATE:    17/08/01 03:58:36 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

At 21:32:04.55 UT on 2017-07-30, the Swift Burst Alert Telescope (BAT)
detected another pulse from the new Galactic source Swift J181723.1-164300
(trigger= 765422). The first trigger on this source occurred on 2017-07-28
(Barthelmy et al., GCN Circ. 21369 and 21385). Due to the higher trigger
threshold set after the first trigger, this detection did not result in a regular
BAT trigger.

Subsequent ground analysis using the data set from T-2 to T+8 sec from
the recent telemetry downlink finds the source at a location of
RA, Dec = 274.320, -16.700 deg which is
   RA(J2000)  =  18h 17m 16.9s
   Dec(J2000) = -16d -41' -60.0"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
This location is consistent with the one found by the previous trigger.
The partial coding was 92%.

The mask-weighted light curve shows a weak pulse that starts at ~T0 and lasts
beyond the end of event data.

The spectral fit of the time-averaged spectrum from T+0.0 to T+8.0 sec
using a simple power-law model gives a power law index of 4.24 +- 0.60.
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+5.10 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 results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/765422/BA/