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Constraints on the 3-30 MeV emission of Seyfert galaxies
M. Maisack, K. Mannheim, W. Collmar
Seyfert galaxies have not been detected by COMPTEL on the Compton Gamma Ray Observatory (CGRO) in the energy range 0.75-3 MeV, placing upper limits on their emission which are more…
The Gamma Ray Burst Rate at High Photon Energies
Karl Mannheim, Dieter Hartmann, Burkhardt Funk
Some gamma-ray burst (GRB) spectra exhibit high energy tails with the highest photon energy detected at 18 GeV. The spectral slope of the high-energy tails is sufficiently flat in…
Beacons at the Gamma Ray Horizon
K. Mannheim, S. Westerhoff, H. Meyer +1
Blazars with redshifts z<0.1 are likely candidates for detection at energies in the range 300 GeV - 50 TeV with Cerenkov telescopes and scintillator arrays. We present gamma-ray fl…
Search for Supergalactic Anisotropies in the 3B Catalog
Dieter H. Hartmann, Michael S. Briggs, Karl Mannheim
The angular distribution of GRBs is isotropic, while the brightness distribution of bursts shows a reduced number of faint events. These observations favor a cosmological burst ori…