Diffuse galactic hard X-ray and low-energy gamma-ray continuum

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We summarize some recent results related to observations and interpretation of hard X-ray and low-energy 7-ray diffuse Galactic continuum emission. Combined spectra based on data from OSSE, COMPTEL and EGRET are presented. In the energy range 1-30 MeV covered by COMPTEL the spectrum of the diffuse emission has been measured and is consistent with a combination of bremsstrahlung and inverseCompton emission; spatial analysis shows strong evidence for a component with a wide latitude extent which is plausibly identified with inverse-Compton. Molecular hydrogen appears to be only a weak γ-ray emitter at low energies, which may indicate reduced MeV cosmic-ray electron density in molecular clouds. New data on the hard X-ray diffuse Galactic emission from OSSE indicates the need for a dramatic low-energy upturn in the electron spectrum, or for some other additional component of γ-ray emission. The interstellar electron spectrum has been computed using a diffusive halo model and the resulting bremsstrahlung and inverse-Compton emission is compared with the observations.

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Astronomy and Astrophysics Supplement Series

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