  We investigated the multiband emission from the pulsar binaries XSS
J12270-4859, PSR J2039-5617, and PSR J2339-0533, which exhibit orbital
modulation in the X-ray and gamma-ray bands. We constructed the sources'
broadband spectral energy distributions and multiband orbital light curves by
supplementing our X-ray measurements with published gamma-ray results, and we
modeled the data using intra-binary shock (IBS) scenarios. While the X-ray data
were well explained by synchrotron emission from electrons/positrons in the
IBS, the gamma-ray data were difficult to explain with the IBS components
alone. Therefore, we explored other scenarios that had been suggested for
gamma-ray emission from pulsar binaries: (1) inverse-Compton emission in the
upstream unshocked wind zone and (2) synchrotron radiation from
electrons/positrons interacting with a kilogauss magnetic field of the
companion. Scenario (1) requires that the bulk motion of the wind substantially
decelerates to ~1000km/s before reaching the IBS for increased residence time,
in which case formation of a strong shock is untenable, inconsistent with the
X-ray phenomenology. Scenario (2) can explain the data if we assume the
presence of electrons/positrons with a Lorentz factor of ~$10^8$ (~0.1 PeV)
that pass through the IBS and tap a substantial portion of the pulsar voltage
drop. These findings raise the possibility that the orbitally-modulating
gamma-ray signals from pulsar binaries can provide insights into the flow
structure and energy conversion within pulsar winds and particle acceleration
nearing PeV energies in pulsars. These signals may also yield greater
understanding of kilogauss magnetic fields potentially hosted by the low-mass
stars in these systems.
