Gamma‐Ray Lines of Carbon and Oxygen from Orion

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Abstract
The gamma-ray lines from the Orion complex observed by the COMPTEL instrument are interpreted as related to the de-excitation in flight of accelerated oxygen and carbon in a molecular cloud, essentially composed of hydrogen and helium. The shape and the intensity of the lines are two constraints for any hypothesis concerning the acceleration/injection process. Using an update of the involved gamma-production cross sections, two models of acceleration are examined, leading to a shock spectrum or a supernova spectrum for the accelerated carbon and oxygen. Although the actual error bars in the published COMPTEL spectrum are too large to draw firm conclusions at this stage, our interpretation of the COMPTEL data is in better agreement with a spectral shape related to the ejection of those nuclei by a Type Ic supernova.