Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: iota Horologi, the first coronal activity cycle in a young solar-like
  star   Context: The shortest chromospheric (Ca II H&K) activity cycle (1.6 yr) has
been recently discovered in the young (~600 Myr) solar-like star iota Hor.
Coronal X-ray activity cycles have only been discovered in a few stars other
than the Sun, all of them with an older age and a lower activity level than
iota Hor. Aims: We intended to find the X-ray coronal counterpart of the
chromospheric cycle for i Hor. This represents the first X-ray cycle observed
in an active star, as well as the paradigm of the first coronal cycles in the
life of a solar-like star. Methods: We monitored i Hor with XMM-Newton
observations spanning almost two years. The spectra of each observation are fit
with two-temperature coronal models to study the long-term variability of the
star. Results: We find a cyclic behavior in X-rays very similar to the
contemporaneous chromospheric cycle. The continuous chromospheric monitoring
for more than three cycle lengths shows a trend toward decreasing amplitude,
apparently modulated by a longer term trend. The second cycle is disrupted
prior to reaching its maximum, followed by a brief episode of chaotic
variability before the cyclic behavior resumes, only to be disrupted again
after slightly more than one cycle. Conclusions: We confirm the presence of an
activity cycle of ~1.6 yr in i Hor both in X-rays and Ca II H&K. It is likely
subject to the modulation of a longer, not yet constrained second cycle. The
1.6 yr cycle is the shortest coronal one observed to date, and i Hor represents
the most active star for which a coronal activity cycle has been found. This
cycle is probably representative of the first coronal cycles in the life of a
solar-like star, at the age when life started on Earth.

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The categories of this paper are: acc-phys
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas