On the Multiplicity of the O-Star Cyg OB2 #8a and its Contribution to the γ-ray Source 3EG J2033+4118 |
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Authors: | Michael De Becker Gregor Rauw Jean-Pierre Swings |
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Affiliation: | 1. Institut d’Astrophysique et de Géophysique, Université de Liège, 17, Allée du 6 Ao?t, B5c, Sart Tilman, Belgium
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Abstract: | We present the results of an intensive spectroscopic campaign in the optical waveband revealing that Cyg OB2 #8A is an O6+O5.5 binary system with a period of about 21.9 days. Cyg OB2 #8A is a bright X-ray source, as well as a non-thermal radio emitter. We discuss the binarity of this star in the framework of a campaign devoted to the study of non-thermal emitters, from the radio waveband to γ-rays. In this context, we attribute the non-thermal radio emission from this star to a population of relativistic electrons, accelerated by the shock of the wind-wind collision. These relativistic electrons could also be responsible for a putative γ-ray emission through inverse Compton scattering of photospheric UV photons, thus contributing to the yet unidentified EGRET source 3EG J2033+4118. Based partly on data Obtained at the Observatoire de Haute-Provence, France. |
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Keywords: | binaries: spectroscopic stars: individual: Cyg OB2 #8A stars: early-type radiation mechanisms: non-thermal |
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