M. Böttcher and R. Schlickeiser,
Astronomy & Astrophysics, 302, L17 (1995)
The yield of electron-positron and electron-electron bremsstrahlung in the hard X-ray and gamma-ray regime from leptonic jets in active galactic nuclei is calculated. We argue that in the case of ultrarelativistic jets where the intrinsic particle spectra have lower cutoffs >~ 5 the contribution of electron-positron and electron-electron bremsstrahlung overwhelms the yield of pair annihilation radiation which poses severe constraints on models trying to explain spectral bumps at MeV energies observed in the gamma-ray spectra of many AGNs by a broadened, blue shifted annihilation line from an ultrarelativistic pair plasma. It is demonstrated that bremsstrahlung emission from a power-law distribution of relativistic particles could as well be responsible for spectral breaks > 0.5 at MeV energies with the instantaneous photon spectra having a flat shape (spectral index 1.1 in photon number spectrum) at photon energies well below the break.