Modeling the high-energy radiation in gamma-ray binaries

Abstract

Gamma-ray binaries are orbital modulated gamma-ray sources in the Galaxy detected both at GeV and TeV energies. The high-energy radiation may come from the interaction of energetic electrons injected by a young pulsar and photons from the massive companion star. We present a model for the production of high-energy radiation where emission, absorption and pair cascading are considered. New observations of LS I +61 303 by the Fermi Space Telescope revealed an exponential cut-off in the spectrum at a few GeV, inconsistent with gamma-gamma absorption. Electrons radiating at GeV and TeV have probably two different origins. We investigate whether the emission from the unshocked pulsar wind explains the GeV component in LS I +61 303.