Gamma-ray predictions for the very massive colliding-wind binary HD 93129A

Colliding-wind binaries have long been expected to be a class of γ-ray sources; however, up to date only η-Carinae has been firmly confirmed as such, and recently WR 11 was also associated with a Fermi source. In this work we study the possible high-energy emission arising from the binary stellar system HD 93129A, one of the most massive binaries in the Galaxy. This system presents non-thermal radio emission produced in the wind-collision region (WCR). We developed a broadband non-thermal radiative model for the WCR taking into account the evolution of the accelerated particles streaming along the shocked region, their emission by different radiative processes, and the attenuation of this radiation propagating through the local matter and electromagnetic fields. Our model is able to reproduce the radio data and it predicts that the non-thermal emission in hard X-rays and γ-rays from HD 93129A will increase in the near future, as the system approaches periastron. In particular, we show that for efficient particle acceleration and low magnetic fields in the WCR, HD 93129A should be detected by Fermi in the next few years.