Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radio emission from the X-ray pulsar Her X-1: a jet launched by a strong
  magnetic field neutron star?   Her X-1 is an accreting neutron star in an intermediate-mass X-ray binary.
Like low-mass X-ray binaries (LMXBs), it accretes via Roche-lobe overflow, but
similar to many high-mass X-ray binaries containing a neutron star, Her X-1 has
a strong magnetic field and slow spin. Here, we present the discovery of radio
emission from Her X-1 with the Very Large Array. During the radio observation,
the central X-ray source was partially obscured by a warped disk. We measure a
radio flux density of $38.7 \pm 4.8$ $\mu$Jy at $9$ GHz but can not constrain
the spectral shape. We discuss possible origins of the radio emission, and
conclude that coherent emission, a stellar wind, shocks and a propeller outflow
are all unlikely explanations. A jet, as seen in LMXBs, is consistent with the
observed radio properties. We consider the implications of the presence of a
jet in Her X-1 on jet formation mechanisms and on the launcing of jets by
neutron stars with strong magnetic fields.

3
The categories of this paper are: physics
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-bio
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The categories of this paper are: funct-an