COMPTEL Gamma-Ray Observations of X-Ray Binaries

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Session 29 -- Gamma Ray Astrophysics
Oral presentation, Wednesday, January 12, 2:15-3:45, Salon III Room (Crystal Gateway)

[29.05] COMPTEL Gamma-Ray Observations of X-Ray Binaries

M.L. McConnell, D. Forrest, J. Ryan (UNH), W. Collmar, V. Sch\"onfelder, H. Steinle, A. Strong (MPE), R. van Dijk, W. Hermsen (SRON-Leiden), K. Bennett (SSD/ESA)

The COMPTEL experiment on the {\sl Compton Gamma-Ray Observatory} (CGRO), which operates in 0.75-30 MeV energy range, has surveyed the entire sky since its launch in April, 1991. To date, at least two of the sources detected by COMPTEL are X-ray binaries: Cygnus X-1 and Nova Persei (GRO J0422+32). Generally speaking, the observed emission from these sources falls off rapidly near 1 MeV. The spectrum of Cygnus X-1 is observed to energies in excess of 2 MeV with a shape which is inconsistent with standard Comptonization models. The spectrum of Nova Persei, on the other hand, suggests a hardening of the spectrum near 1 MeV, somewhat reminiscent of the type of spectra previously reported by HEAO-3 for Cygnus X-1 and 1E1740.7-2942. There is some evidence (both theoretical and experimental) suggesting that several more X-ray binaries may be visible with COMPTEL. Here we shall review the latest results from both Cygnus X-1 and Nova Persei and report on our efforts to detect emission from other X-ray binary systems. This includes both Cygnus X-3 as well as a selected sample of galactic black hole candidates.

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