Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Chandra Deep Field-North Survey: XVII. Evolution of magnetic
  activity in old late-type stars   The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray
survey is used to identify and characterize the X-ray emission from old
high-latitude main sequence Galactic stars. Our principal goal is to
investigate the expected long-term decay of magnetic activity of late-type
stars due to the gradual spindown of stellar rotation from a magnetized stellar
wind. Eleven X-ray sources constitute a well-defined sample of 2 G, 2 K0-K4,
and 7 M2-M5 stars with median distance around 300 pc. X-ray luminosities are
typically log Lx ~ 27 erg/s and is dominated by flares rather than quiescent
coronal emission. Models of the population indicates that the CDF-N stars are
the most magnetically active old disk stars. A substantial decline in X-ray
luminosities over the 1<t<11 Gyr age interval is required. This is the first
demonstration that the coronal and flaring components of stellar magnetic
activity -- and presumably the interior magnetic dynamos responsible for the
reconnecting fields at the stellar surface -- exhibit long-term decay over the
age of the Galactic disk. The model that best fits the magnitudes, spectral
types and X-ray luminosities of the sample has Lx ~ 1/t^2 erg/s which is faster
than the 1/t decay rate predicted from widely accepted rotational spindown
rates and X-ray-activity relations.

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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: chem-ph
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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: nucl-th
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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: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: math
0
The categories of this paper are: hep-ph