  Pulsar winds have been shown to be preferred sites of particle acceleration
and high-energy radiation. Numerous studies have been conducted to better
characterize the general structure of such relativistic plasmas in isolated
systems. However, many pulsars are found in binary systems and there are
currently no ab initio models available that would include both the pulsar
magnetosphere and the wind of the pulsar in interaction with a spherical
companion. We investigate the interaction between a pulsar wind and a companion
to probe the rearrangement of the pulsar wind, assess whether it leads to an
enhancement of particle acceleration, and predict the high-energy radiative
signature that stems from this interaction. We perform two-dimensional
equatorial particle-in-cell simulations of an inclined pulsar surrounded by a
spherical, unmagnetized, perfectly conducting companion settled in its wind. We
find that the presence of the companion significantly alters the structure of
the wind. When the companion lies beyond the fast magnetosonic point, a shock
is established and the perturbations are advected in a cone behind the
companion. We observe an enhancement of particle acceleration due to forced
reconnection as the current sheet reaches the companion surface. Hence,
high-energy synchrotron radiation is also amplified. The orbital light curves
display two broad peaks reaching up to 14 times the high-energy pulsed flux
emitted by an isolated pulsar magnetosphere. These effects increase with the
growth of the companion size and with the decrease of the pulsar-companion
separation. The present study suggests that a pulsar wind interacting with a
companion induces a significant enhancement of high-energy radiation that takes
the form of an orbital-modulated hollow cone of emission, which should be
detectable by galactic-plane surveys, possibly with long-period radio transient
counterparts.
