Hadronic gamma-ray production in microquasars with equatorial winds

Abstract

Microquasars are accreting X-ray binary systems with non thermal radio jets. When the primary is a highmass early type star, the compact object accretes from the stellar wind. In some cases, like LS I +61 303, the wind forms an equatorial disk and the secondary moves through it. In such a situation a strong interaction between the relativistic flow and the dense wind material is unavoidable and could result in the generation of high energy emission. This is particularly interesting since microquasars have been recently confirmed to be high energy γ ray sources. We present here a hadronic model for gamma-ray production in this kind of systems, with a specific application to the case of LS I +61 303. We calculate the gamma-ray emission originated in pp interactions between relativistic protons in the jet and cold protons from the wind. The emission from secondary electron-positron pairs is estimated as well. After taking into account opacity effects on the gammarays introduced by the different photons fields, we present high-energy spectral predictions that can be tested with the new generation Cherenkov telescopes like MAGIC and HESS