Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A magnetically collimated jet from the evolved star W43A   We present the first direct measurements of the magnetic field strength and
direction in a collimated jet from an evolved star on its way to become a
planetary nebula. Very Long Baseline Array (VLBA) observations of the linear
and circular polarization of the water masers in the collimated jet of W43A
reveal a strong toroidal magnetic field, indicating that the jet is
magnetically collimated. The magnetic field strength in the jet extrapolated
back to the stellar surface yields a surface field of several Gauss, consistent
with the measurements of maser polarization in a large sample of evolved stars.
The origin of the magnetic field is yet unknown, although the jet precession
might point to the existence of a heavy planet or stellar companion. This is
the first direct observational evidence for magnetic collimation in the jets,
that likely play an important role in shaping planetary nebulae.

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The categories of this paper are: bayes-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci