The contribution of untriggered GRBs to the
γ-ray
background
can be estimated in a number of ways, but all depend on modeling, or
inferring from observations, the typical high-energy GRB spectra. For
the optimistic case that the TeV flux made by a GRB is
10 &215; greater than the MeV flux, then the superpositions of GRB
emissions are found to make
10% of the
γ-ray
background after cascading from high energies into the GeV band
[9].
If one instead relies on observations of EGRET
spark-chamber GRBs that show that the fluence in the EGRET band is
only 10% of the
fluence in the BATSE band, then GRBs are found to give very little
(
1%) contribution
to the
γ-ray
background
[25].
This neglects the contributions
of short, hard GRBs and low luminosity GRBs, but since these have
small fluences and all-sky rates, they are unlikely to make
a significant contribution to the
γ-ray
background.
It hardly needs to be mentioned that GLAST observations of the high-energy emission from GRBs will provide crucial information to determine the share of the background γ-ray intensity provided by GRBs.