Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: ECHA J0843.3-7905: Discovery of an 'old' classical T Tauri star in the
  eta Chamaeleontis cluster   A limited-area survey of the eta Chamaeleontis cluster has identified 2 new
late-type members. The more significant of these is ECHA J0843.3-7905 (= IRAS
F08450-7854), a slowly-rotating (P = 12 d) M2 classical T Tauri (CTT) star with
a spectrum dominated by Balmer emission. At a distance of 97 pc and cluster age
of approx 9 Myr, the star is a nearby rare example of an 'old' CTT star and
promises to be a rewarding laboratory for the study of disk structure and
evolution in pre-main sequence (PMS) stars. The other new member is the M4
weak-lined T Tauri (WTT) star ECHA J0841.5-7853, which is the lowest mass (M =
0.2 M_sun) primary known in the cluster.

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The categories of this paper are: cs
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The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
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The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org