TITLE: GCN CIRCULAR NUMBER: 8408 SUBJECT: GRB 081024B: Fermi Gamma-ray Burst Monitor detection DATE: 08/10/25 19:00:20 GMT FROM: Valerie Connaughton at MSFC Valerie Connaughton and Michael Briggs (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 21:22:40.86 UT on 24 October 2008, the Fermi Gammay-Ray Burst Monitor (GBM) triggered on GRB 081024B (trigger 246576161 / 081024.891). The calculated location is consistent with the Fermi LAT-detected GRB reported by N. Omodei in GCN Circular 8407. This GRB was about 800 ms long with 2 main peaks. The first peak lasted 200 ms and its spectrum is best fit using a power-law index with an exponential cutoff. The power-law index is -0.70 ± 0.13, and the cutoff energy, parameterized as EPeak, is 1583 ± 520 keV. The seond peak lasted 600 ms and is best fit by a power-law spectrum with an index of -1.28 ± 0.04. The fluence between 50 and 300 keV of this short burst is 3.4 ± 0.1 x 10-7 erg/cm2, with a peak flux measured over a 64 ms timescale of of 4.2 ± 0.2 photons/cm2/sec. Between 15 and 150 keV the 64 ms peak flux is 7.4 ± 0.4 photons/cm2/sec. The analysis results presented above are preliminary and further analysis is being performed; the final results will be published in the GBM GRB Catalog."