γ-ray emission above 700 keV from the direction of Centaurus A was detected during a balloon flight with the MPI Compton telescope. The statistical significance of the source detection is 4.1 σ. The location of the source, the profile of the derived source image, and the intensity and shape of the derived energy spectrum strongly suggest that the detected radiation is related to Cen A. The energy spectrum extends into the MeV range at least up to 8 MeV and connects well to the power-law spectrum, which so far has been measured up to several hundred keV. The hard X-ray/soft γ-ray spectrum can be interpreted as a thermal Comptonization spectrum.
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Ballmoos et al. (1987) studied this question.