TITLE:   GCN CIRCULAR
NUMBER:  19998
SUBJECT: GRB 161004B: Fermi GBM detection
DATE:    16/10/05 16:51:33 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007@uah.edu>

R. Hamburg (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 23:07:54.79 UT on 04 October 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 161004B (trigger 497315278 / 161004964)
which was also detected by the Swift BAT
(D'Ai et al. 2016, GCN 19987)
The GBM on-ground location is consistent with the Swift position.

The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux
of the GRB. This ARR was accepted and the spacecraft slewed to the GBM
in-flight
location. The initial angle from the Fermi LAT boresight to
the Swift location is 69 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 14 s (50-300 keV).
The time-averaged spectrum from T0-0.0 s to T0+18.4 s is
best fit by a Band function with Epeak = 132 +/- 6 keV,
alpha = -0.75 +/- 0.04, and beta = -2.4 +/- 0.1.

The event fluence (10-1000 keV) in this time interval is
(1.877 +/- 0.039)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.7 s in the 10-1000 keV band
is 15.4 +/- 0.4 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."