TITLE:   GCN CIRCULAR
NUMBER:  18220
SUBJECT: GRB 150831B: Fermi GBM detection
DATE:    15/09/01 04:53:10 GMT
FROM:    Peter Veres at ELTE,Budapest  <veresp@gmail.com>

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

"At 22:19:27.158 UT on 31 August 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150831B (trigger 462752371 / 150831930)
which was also detected by the Swift/BAT and XRT
(Marshall et al. 2015, GCN 18215 and Evans et al. 2015, GCN 18217)
The GBM on-ground location is consistent with the Swift position.


The angle from the Fermi LAT boresight at the GBM trigger time is 96
degrees.


The GBM light curve has a duration (T90) of about 13.8 s (50-300 keV).
The time-averaged spectrum from T0-4.0 s to T0+6.3 s is
adequately fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.93 +/- 0.12 and
the cutoff energy, parameterized as Epeak, is 82.3 +/- 5.5 keV.


The event fluence (10-1000 keV) in this time interval is
(2.51 +/- 0.11)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 9.1 +/- 0.4 ph/s/cm^2.

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