Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Resolved, expanding jets in the Galactic black hole candidate XTE
  J1908+094   Black hole X-ray binaries undergo occasional outbursts caused by changing
inner accretion flows. Here we report high-angular resolution radio
observations of the 2013 outburst of the black hole candidate X-ray binary
system J1908+094, using data from the VLBA and EVN. We show that following a
hard-to-soft state transition, we detect moving jet knots that appear
asymmetric in morphology and brightness, and expand to become laterally
resolved as they move away from the core, along an axis aligned approximately
$-11$\degree\ east of north. We initially see only the southern component,
whose evolution gives rise to a 15-mJy radio flare and generates the observed
radio polarization. This fades and becomes resolved out after 4 days, after
which a second component appears to the north, moving in the opposite
direction. From the timing of the appearance of the knots relative to the X-ray
state transition, a 90\degree\ swing of the inferred magnetic field
orientation, the asymmetric appearance of the knots, their complex and evolving
morphology, and their low speeds, we interpret the knots as working surfaces
where the jets impact the surrounding medium. This would imply a substantially
denser environment surrounding XTE J1908+094 than has been inferred to exist
around the microquasar sources GRS 1915+105 and GRO J1655-40.

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The categories of this paper are: q-bio
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
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The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex