  PSR B1259-63/LS 2883 is a very high energy (VHE; E > 100 GeV) gamma-ray
emitting binary consisting of a 48 ms pulsar orbiting around a Be star with a
period of 3.4 years. The Be star features a circumstellar disk which is
inclined with respect to the orbit in such a way that the pulsar crosses it
twice every orbit. The circumstellar disk provides an additional field of
target photons which may contribute to inverse Compton scattering and
gamma-gamma absorption, leaving a characteristic imprint in the observed
spectrum and light curve of the high energy emission. We study the signatures
of Compton-supported, VHE gamma-ray induced pair cascades in the circumstellar
disc of the Be star and their possible contribution to the GeV flux. We also
study a possible impact of the gamma-gamma absorption in the disk on the
observed TeV light curve. We show that the cumulative absorption of VHE
gamma-rays in stellar and disk photon fields can explain the modulation of the
flux at the periastron passage.
