Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The large-scale magnetic field of Proxima Centauri near activity maximum   We report the detection of a large-scale magnetic field at the surface of the
slowly-rotating fully-convective M dwarf Proxima Centauri. Ten circular
polarization spectra, collected from April to July 2017 with the HARPS-Pol
spectropolarimeter, exhibit rotationally-modulated Zeeman signatures suggesting
a stellar rotation period of $89.8 \pm 4.0$ d. Using Zeeman-Doppler Imaging, we
invert the circular polarization spectra into a surface distribution of the
large-scale magnetic field. We find that Proxima Cen hosts a large-scale
magnetic field of typical strength 200 G, whose topology is mainly poloidal,
and moderately axisymmetric, featuring, in particular, a dipole component of
135 G tilted at 51$^{\circ}$ to the rotation axis. The large-scale magnetic
flux is roughly 3 times smaller than the flux measured from the Zeeman
broadening of unpolarized lines, which suggests that the underlying dynamo is
efficient at generating a magnetic field at the largest spatial scales. Our
observations occur $\sim$1 yr after the maximum of the reported 7 yr-activity
cycle of Proxima Cen, which opens the door for the first long-term study of how
the large-scale field evolves with the magnetic cycle in a fully-convective
very-low-mass star. Finally, we find that Proxima Cen's habitable zone planet,
Proxima-b, is likely orbiting outside the Alfv\`en surface, where no direct
magnetic star-planet interactions occur.

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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: physics
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The categories of this paper are: ao-sci