High-mass binaries hosting young pulsars can be powerful gamma-ray emitters.
The stellar wind of the massive star in the system is expected to be clumpy.
Since the high-energy emission comes from the pulsar-star wind interaction, the
presence of clumps can affect the spectrum and variability of this radiation.
We look for the main effects of the clumps on the two-wind interaction region
and on the non-thermal radiation. A simple analytical model for the two-wind
interaction dynamics was developed accounting for the lifetime of clumps under
the pulsar-wind impact. This time plays a very important role with regard to
the evolution of the clump, the magnetic field in the clump-pulsar wind
interaction region, and the non-radiative and radiative cooling of the
non-thermal particles. We also computed the high-energy emission produced at
the interaction of long-living clumps with the pulsar wind. For reasonable
parameters, the clumps will induce small variability on the X-ray and gamma-ray
radiation. Sporadically, large clumps can reach closer to the pulsar increasing
the magnetic field, triggering synchrotron X-ray flares and weakening other
emission components like inverse Compton. The reduction of the emitter size
induced by clumps also makes non-radiative losses faster. Stellar wind clumps
can also enhance instability development and matter entrainment in the shocked
pulsar wind when it leaves the binary. Growth limitations of the clumps from
the wind acceleration region may imply that a different origin for the largest
clumps is required. The large-scale wind structures behind the observed
discrete absorption components in the UV may be the source of these large
clumps. The presence of structure in the stellar wind can produce substantial
energy-dependent variability and should not be neglected when studying the
broadband emission from high-mass binaries hosting young pulsars.Comment: 8 pages, 4 figures, accepted for publication in Astronomy and
Astrophysics (minor corrections after proofs
