TITLE: GCN CIRCULAR NUMBER: 9974 SUBJECT: GRB 090927: Fermi GBM observation DATE: 09/09/30 13:01:46 GMT FROM: David Gruber at MPE D. Gruber (MPE), E. Bissaldi (MPE) and S. McBreen (UCD/MPE) report on behalf of the Fermi GBM Team: "At 10:07:17.21 UT on 27 September 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090927 (trigger 275738839 / 090927422), which was also detected by the Swift-BAT (Grupe al. 2009, GCN 9945). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 85 degrees. The GBM light curve consists of one weak pulse with a duration of about 2 seconds. The time-averaged spectrum from T0-0.256 s to T0+0.896 s is adequately fit by a simple power law function with index -1.47 +/- 0.06 (C-stat 330 for 239 d.o.f.). The event fluence (8-1000 keV) in this time interval is (6.1 +/- 0.5)E-07 erg/cm^2. The 128-msec peak photon flux measured starting from T0-0.128 s in the 8-1000 keV band is 7.2 +/- 0.9 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."