  Current generation of ground based gamma-ray telescopes observed dozens of
sources of photons above 100 TeV. Supernova remnants, pulsar wind nebulae,
young stellar clusters and superbubbles are considered as possible sites of
PeV-regime particles producing the radiation. Another possible source of PeV
particles could be gamma-ray binary systems. In these systems, a strong
relativistic outflow from a compact object (neutron star or black hole)
collides with the dense wind from a massive companion early-type star.
Gamma-ray binaries are observed from radio to high energy gamma-rays as
luminous non-thermal sources. Apart from acceleration of very high energy
leptons producing most of the non-thermal radiation, these systems may also
efficiently accelerate protons. We present here the results of numerical
simulation of the PeV-regime proton acceleration in gamma-ray binaries. The
simulation is based on relativistic MHD modeling of local flows of magnetized
plasma in the region of interaction of two colliding winds. We then inject 0.1
PeV protons into the system and directly follow their trajectories to
demonstrate that they are accelerated to energies above PeV. High magnetization
of the wind of the young massive star providing a Gauss range field in the
winds interaction region is of paramount importance for the acceleration of
protons above PeV. The maximum energies of protons accelerated by colliding
winds in gamma ray binaries can significantly exceed the energy of the pulsar
potential's drop, which limits from above the energy of particles accelerated
by an isolated pulsar.
