TITLE:   GCN CIRCULAR
NUMBER:  21872
SUBJECT: GRB 170912B: Fermi GBM observations
DATE:    17/09/12 16:05:35 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P Veres (UAH), A von Kienlin (MPE) and C Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 06:33:46.91 UT on 12 September 2017, the Fermi Gamma-Ray Burst
Monitor triggered and located GRB 170912B (trigger 526890831 /
170912273) which was also detected by the Swift satellite (LaPorte et
al., GCN 21864). The GBM on-ground location is consistent with the
Swift position.

The angle from the Fermi LAT boresight at the GBM trigger
time is 39 degrees.

The GBM light curve shows multiple overlapping peaks
with a duration (T90) of about 13.3 s (50-300 keV).
The time-averaged spectrum from T0-1.7 s to T0+13.7 s is
best fit by a Band function with Epeak = 45.2 +/- 6.0 keV,
alpha = -0.88 +/- 0.23, and beta = -2.13 +/- 0.06.

The event fluence (10-1000 keV) in this time interval is
(4.5 +/- 0.2)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.1 s in the 10-1000 keV band
is 8.7 +/- 0.3 ph/s/cm^2.

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