GeV-TeV γ-ray light curves expected in the IC e± pair cascade model for massive binaries:: application to LS 5039

Context. TeV gamma-ray emission from two massive binaries of the microquasar type, LS 5039 and LS I + 61 degrees 303, show clear variability with their orbital periods. Aims. Our purpose is to calculate the GeV and TeV gamma-ray light curves from the massive binary LS 5039, which are expected in the specific inverse Compton e(+/-) pair cascade model. This model has successfully predicted the basic features of the high energy gamma-ray emission from LS 5039 and LS I + 61 degrees 303. Methods. In the calculations we apply the Monte Carlo code, which follows the IC e(+/-) pair cascade in the anisotropic radiation of the massive star. Results. The gamma-ray light curves and spectra are obtained for different parameters of the acceleration scenario and the inclination angles of the binary system. We find that the GeV and TeV gamma-ray light curves should be anti-correlated. This feature can be tested in the near future by the simultaneous observations of LS 5039 with the AGILE and GLAST telescopes in GeV energies and the Cherenkov telescopes in the TeV energies. This model also predicts a broad maximum in the TeV gamma-ray light curve between the phases similar to 0.4-0.8 consistently with the observations of LS 5039 by the HESS telescopes. Moreover, we predict an additional dip in the TeV light curve for large inclination angles similar to 60 degrees. This feature could serve as a diagnostic for independently measuring the inclination angle of this binary system indicating also the presence of a neutron star in LS 5039.