Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectropolarimetric observations of the transiting planetary system of
  the K dwarf HD 189733   With a Jupiter-mass planet orbiting at a distance of only 0.031 AU, the
active K2 dwarf HD 189733 is a potential candidate in which to study the
magnetospheric interactions of a cool star with its recently-discovered
close-orbiting giant planet. We decided to explore the strength and topology of
the large-scale magnetosphere of HD 189733, as a future benchmark for
quantitative studies for models of the star/planet magnetic interactions. To
this end, we used ESPaDOnS, the new generation spectropolarimeter at the
Canada-France-Hawaii 3.6m telescope, to look for Zeeman circular polarisation
signatures in the line profiles of HD 189733 in 2006 June and August. Zeeman
signatures in the line profiles of HD 189733 are clearly detected in all
spectra, demonstrating that a field is indeed present at the surface of the
star. The Zeeman signatures are not modulated with the planet's orbital period
but apparently vary with the stellar rotation cycle. The reconstructed
large-scale magnetic field, whose strength reaches a few tens of G, is
significantly more complex than that of the Sun; it involves in particular a
significant toroidal component and contributions from magnetic multipoles of
order up to 5. The CaII H & K lines clearly feature core emission, whose
intensity is apparently varying mostly with rotation phase. Our data suggest
that the photosphere and magnetic field of HD 189733 are sheared by a
significant amount of differential rotation. Our initial study confirms that HD
189733 is an optimal target for investigating activity enhancements induced by
closely orbiting planets. More data are needed, densely covering both the
orbital and rotation cycles, to investigate whether and how much the planet
contributes to the overall activity level of HD 189733.

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The categories of this paper are: plasm-ph
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys