TITLE:   GCN CIRCULAR
NUMBER:  21813
SUBJECT: GCN GRB 170903A
DATE:    17/09/04 20:48:43 GMT
FROM:    Francesco Berlato at MPE  <fberlato@mpe.mpg.de>

F Berlato (MPE) and C Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 12:49:07.79 UT on 3 September 2017, the Fermi Gamma-Ray Burst 
Monitor
triggered and located GRB 170903A (trigger 526135752 / 170903534), 
which
was also detected by the Swift/BAT (Markwardt et al., GCN 21793).

The Swift localization, consistent with the GBM one, is RA = 254.532 
deg,
DEC = 34.985 deg (J2000, equivalent to 16h 58m 7.7s, +34d 59' 7.5"),
with an uncertainty of 1.3 arcmin (radius, sys+stat, 90% containment).

The angle from the Fermi LAT boresight at the GBM trigger time is 93 
deg.

The GBM light curve shows two pulses with a duration (T90) of
about 25 s (50-300 keV). The time-averaged spectrum from
T0-1.5 s to T0+25.5 s is adequately fit by a Comptonized model,
with index  -1.56 +/- 0.10 and Epeak 124 +/- 33 keV .
The event fluence (10-1000 keV) in the time interval is
(4.34 +/- 0.54)E-06 erg/cm^2. The 1-sec peak photon flux (10-1000 keV)
measured starting from T0-1.5 s is (5.80 +/- 0.36) ph/s/cm^2.

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