GAMMA-RAY BURST PREDICTIONS FOR THE FERMI GAMMA RAY SPACE TELESCOPE

Results of a phenomenological model to estimate the gamma-ray burst (GRB) detection rate by the Fermi Gamma-Ray Space Telescope are reported. This estimate is based on the Burst and Transient Source Experiment (BATSE) 4B GRB fluence distribution, the mean ratio of fluences measured at 100 MeV-5 GeV with Energetic Gamma-Ray Experiment Telescope (EGRET) and at 20 keV-2 MeV with BATSE, and the mean EGRET GRB spectrum for the five EGRET spark-chamber GRBs. For a 10% fluence ratio and a number spectral index alpha(1) = -2 at 100 MeV-5 GeV energies, we estimate a rate of approximate to 20 and 4 GRBs yr(-1) in the Fermi Large Area Telescope field of view (FOV) with at least five photons with energy E > 100 MeV and E > 1 GeV, respectively. We also estimate approximate to 1.5 GRBs yr(-1) in the Fermi FOV where at least one photon with energy E > 10 GeV is detected. For these parameters, we estimate approximate to 1-2 GRBs yr(-1) detected with the Fermi telescope with more than 100 gamma-rays with E greater than or similar to 100 MeV. Comparison predictions for alpha(1) = -2.2, different fluence ratios, and the AGILE gamma-ray satellite are made. Searches for different classes of GRBs using a diagram plotting 100 MeV-10 GeV fluence versus 20 keV-20 MeV fluence is considered as a way to search for separate classes of GRBs and, specifically, spectral differences between the short-hard and long-duration GRB classes, and for hard components in GRBs.