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Session 101 - X-rays and X-ray Bursts.
Display session, Thursday, January 16
Metropolitan Ballroom,
The COMPTEL experiment on the Compton Gamma Ray Observatory, with its large FoV imaging capability, has successfully surveyed the entire sky in the 0.75--30 MeV energy range. Falling within this energy range is the neutron capture line at 2.223 MeV. Various scenarios of accretion onto compact objects predict potentially observable 2.223 MeV line fluxes from X-ray binary systems. For example, unshifted line emission would result from neutron capture in the atmosphere of the compact object's companion star. COMPTEL provides the best opportunity to test such models. Despite the presence of a strong background line at \sim2.2 MeV, COMPTEL provides an unprecedented sensitivity in this energy range. The available data (accumulated over more than 5 years of the CGRO mission) provides a COMPTEL narrow-line sensitivity of better than \sim 1 \times 10^-5 cm^^-2 s^-1. This is approximately an order-of-magnitude below the upper limits which were derived for a few selected objects from data obtained by the SMM Gamma-Ray Spectrometer. This flux level also coincides with the upper range of possible flux values predicted by the published models. Here we shall report on the results of our all-sky imaging effort at 2.223 MeV and, in particular, on a search for (unshifted) 2.223 MeV emission from X-ray binary systems. These latest results represent an improvement over previously-reported results in that we now incorporate all data from the first 5 years of the CGRO mission.
