TITLE: GCN CIRCULAR NUMBER: 8205 SUBJECT: GRB 080905B: Fermi Gamma-ray Burst Monitor detection DATE: 08/09/09 18:15:32 GMT FROM: Narayana Bhat at U Alabama/Huntsville/GBM P. N. Bhat (UAH), W. Paciesas (UAH) and A.J. van der Horst (NASA/ORAU) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 16:55:46 UT on 5 September 2008, the Fermi GBM triggered and located GRB 080905B (trigger 242326547 / 080905705), which was also detected by Swift (Stroh et al., GCN 8182). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 307.1, Dec = -60.2 (J2000 degrees) (equivalent to J2000 20h 28m, -60d 12'), with a statistical uncertainty of 5.7 degree (radius, 1-sigma containment; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight to the GBM localization is 82 degrees. This long GRB consists of one main peak at trigger time, possibly a weak pre-trigger at T-20 s and second peak at T0 + 70 sec and the third from T0+80 sec to T0+110 sec similar to the Swift light curve. The burst duration (in the energy range 20-1000 keV) T90 is about 159 sec. The time-averaged spectrum from T0-20 to T0+110 sec is well fit by a power law function with index -1.75 +/- 0.12.The fluence (20-1000 keV) is 4.1(+/-0.3)E-08 erg/cm2and the peak flux (20-1000 keV) is 0.21 +/- 0.02 ph/cm2/s. The spectral analysis results presented above are preliminary; final results will be published in the Fermi GBM GRB Catalog."