1996A&A...307L..37B

We present modelling results of broad-line γ-ray spectra (from the deexcitation of energetic nuclei), which may apply to γ-ray sources like Orion as detected by COMPTEL. We show that distinct line splitting can occur even if the distribution of fast emitting nuclei is essentially isotropic. The splitting results from the anisotropy of the photon emission in the rest frame of the nuclei, as is seen in accelerator experiments, followed by Doppler shifting. This can have a drastic impact on the interpretation of observed γ-ray spectra. We have modelled in detail an extended source powered by stellar winds and supernovae, but our findings also apply to other candidate sources for broad-line γ-ray emission, such as accretion powered binary systems.