LINE SPLITTING IN BROAD-LINE GAMMA-RAY SPECTROSCOPY OF ORION-LIKE SOURES

We present modelling results of broad-line gamma-ray spectra (from the deexcitation of energetic nuclei), which may apply to gamma-ray sourc es like Orion as detected by COMPTEL. We show that distinct line split ting can occur even if the distribution of fast emitting nuclei is ess entially isotropic. The splitting results from the anisotropy of the p hoton emission in the rest frame of the nuclei, as is seen in accelera tor experiments, followed by Doppler shifting. This can have a drastic impact on the interpretation of observed gamma-ray spectra. We have m odelled in detail an extended source powered by stellar winds and supe rnovae, but our findings also apply to other candidate sources for bro ad-line gamma-ray emission, such as accretion powered binary systems.