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Published online by Cambridge University Press: 04 August 2017
The possibility that the processes responsible for the Cosmic X-ray Background (CXB) would also produce an e−-e+ annihilation feature is examined. Under the assumption that these processes are thermal, the absence of a strong e−-e+ annihilation feature places constraints on the compactness (L/R ratio) of these sources. Observations favor sources of small compactness ratio.