  LS 5039 is an enigmatic high-mass gamma-ray binary which hosts a powerful
O6.5V companion, while the nature of the compact object is still to be
established by multi-wavelength observations analysis. Phase-resolved
multi-instrument spectra of nonthermal emission from LS 5039 are analyzed in
order to produce reliable spectral models, which can be further employed to
select between various scenarios and theoretical models of the binary. The
combined phase-resolved hard X-ray and MeV-range gamma-ray spectra obtained
with XMM-Newton, Suzaku, NuSTAR, INTEGRAL, and Comptel indicate a meaningful
spectral hardening above 50 keV. The spectral break observed in both major
phases of the binary may indicate the presence of two populations of
accelerated leptons in the emitting region, which could originate from the
collision of the O6.5V companion star wind with the flow from yet unidentified
compact object.
