Gamma rays from colliding winds in massive binaries
Binary systems formed by early-type stars with strong winds are known to display variable non-thermal radio emission, thermal X-rays, and, at least in one case (Eta Carina), γ rays. Some of these systems are quite eccentric and the conditions for efficient particle acceleration and γ-ray production might manifest only occasionally. In this paper, I briefly review the physics of colliding wind binaries with emphasis on the observational signatures of non-thermal particle acceleration. I discuss, in particular, the case of the system HD 93129A which is made up of an O2 If* star (the primary) and an O3.5 V star (the secondary). The primary is among the earliest, hottest, most massive, luminous, and windy O stars in the Galaxy. The periastron passage during 2018 will offer an outstanding observational window that will be exploited by an international multi-wavelength campaign.
KeywordsEmission-line stars (Of Be Luminous Blue Variables Wolf–Rayet etc.) γ-Ray sources Mass loss and stellar winds Radiation mechanisms
Mathematics Subject Classification97.30.Eh 98.70.Rz 97.10.Me 95.30.Gv
I thank S. del Palacio, V. Bosch Ramon, P. Benaglia, and M. De Becker for many discussions on this topic. My work was supported by the Helmholtz Association through a Helmholtz International Fellow Award. Additional support was provided by the Argentine agency CONICET (PIP 2014-00338) and the Spanish Ministerio de Economía y Competitividad (MINECO/FEDER, UE) under grant AYA2016-76012-C3-1-P.
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