TITLE:   GCN CIRCULAR
NUMBER:  20572
SUBJECT: GRB 170131A: Fermi GBM observation
DATE:    17/02/01 23:24:55 GMT
FROM:    Bagrat Mailyan at UAH  <bm0054@uah.edu>

B. Mailyan (UAH) and O.J Roberts (NASA-MSFC/USRA) report on
behalf of the Fermi GBM Team:

"At 23:14:59.36 UT on January 31st 2017, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 170131A
(trigger 507597304 /170131969) which was also detected by
the Swift/BAT (Palmer, GCN 20570). The GBM on-ground location
is consistent with the Swift-BAT position.

The angle from the Fermi LAT boresight at the GBM trigger
time using the Swift-BAT position is 18 degrees.

The GBM light curve shows a FRED-like burst with overlapping
pulses with a duration (T90) of about 23 s (50-300 keV).
The time-averaged spectrum from T0-1.0 s to T0+18.4 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.37+/-0.06
and the cutoff energy, parameterized as Epeak, is 209 +/- 34 keV.

The event fluence (10-1000 keV) in this time interval is
(4.56 +/- 0.27)E-06 erg/cm^2. The 1 s peak photon flux measured
starting from T0+15.4 s in the 10-1000 keV band is
4.9 +/- 0.3 ph/s/cm^2.

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