Glast Testing of a Pulsar Model

LS 5039 is one of a handful of X-ray binaries that have been recently detected at high-energy γ-rays, in this case, by the High-Energy Stereoscopy Array (H.E.S.S.). The nature of this system is unknown: both a black hole and a pulsar have been invoked as possible compact object companions. Here we work with a model of the high energy phenomenology of the system in which it is assumed that the companion object is a pulsar rotating around an O6.5V star in the ∼ 3.9 days orbit. The model assumes two different sets of power-law spectral parameters of the interacting primary leptons corresponding to the two orbital phase intervals defined by H.E.S.S. as having different gamma-ray spectra and very-high-energy (VHE) cutoffs. We show the H.E.S.S. phenomenology is completely explained by this model. We present predictions for photons with lower energies (for E > 1 GeV), subject to test in the forthcoming months with the GLAST satellite. We find that GLAST is able to judge on this model within one year. Subject headings: X-ray binaries (individual LS 5039), γ-rays: observations, γ-rays: theory