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The Astrophysical Journal


The American Astronomical Society


We discuss the source of the enhanced carbon and oxygen low-energy cosmic-ray flux in the Orion star-forming region and attribute it to the acceleration of the surface layers of a massive supernova, probably of Type Ib. The gamma rays from Orion are produced by that fast CO ejecta. In this model there would be few Orion-like gamma-ray sources in the Galaxy at any one time. We also postulate that a massive supernova produced the short-lived extinct radioactivities injected into the molecular cloud core that produced the solar system. We find that relative to 26Al the other short-lived extinct radioactivities are excessively produced in massive supernovae but are likely to be more attenuated by postexplosion fallback than 26Al. This is a revival of the supernova trigger hypothesis; to obtain the correct dilutions of the extinct radioactivities, the distance from the supernova to the impacted molecular cloud core must be a few parsecs, and the effective projected collecting area of the cloud must be significantly less than normal core radii.