Paper: astro-ph/0605287
Date: Thu, 11 May 2006 11:15:55 GMT (217kb)

Title: Gamma-ray binaries: pulsars in disguise ?

Authors: Guillaume Dubus

Comments: 20 pages, 20 figures, accepted for publication in A&A
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LS 5039 and LSI +61 303 are unique amongst high-mass X-ray binaries (HMXB)
for their spatially-resolved radio emission and their counterpart at >GeV
gamma-ray energies, canonically attributed to non-thermal particles in an
accretion-powered relativistic jet. The only other HMXB known to emit very high
energy (VHE) gamma-rays, PSR B1259-63, harbours a non-accreting millisecond
pulsar. I investigate whether the interaction of the relativistic wind from a
young pulsar with the wind from its stellar companion, as in PSR B1259-63,
constitutes a viable scenario to explain the observations of LS 5039 and LSI
+61 303. Emission would arise from the shocked pulsar wind material, which then
flows away to large distances in a comet-shape tail, reproducing on a smaller
scale what is observed in isolated, high motion pulsars interacting with the
ISM. Simple expectations for the SED are derived and are shown to depend on few
input parameters. Detailed modelling of the particle evolution is compared to
the observations from radio to TeV energies. Acceleration at the shock provides
high energy electrons that steadily emit synchrotron in X-rays and inverse
Compton scatter stellar light to gamma-rays. Electrons streaming out of the
system emit at IR frequencies and below. The overall aspect of the SEDs is
adequately reproduced for standard values of the parameters. The morphology of
the radio tail can mimic a microquasar jet. Good agreement is found with the
published VLBI map of LS 5039 and predictions are made on the expected change
in appearance with orbital phase. The pulsar wind scenario can provide a
common, viable framework to interpret the emission from all three gamma-ray
binaries.

\\ ( http://arXiv.org/abs/astro-ph/0605287 , 217kb)