Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chromospheric Ca II H and K Emission Among Subdwarfs   Echelle spectra have been obtained of the Ca II H and K lines for a sample of
metal-poor subdwarf stars as well as for a number of nearby Population I dwarfs
selected from among those included in the Mount Wilson HK survey. The main
conclusion of this paper is that Ca II H- and K-line emission does occur among
subdwarfs. It is particularly notable among those subdwarfs with colours of B-V
> 0.75; all such stars observed exhibit chromospheric emission, although
emission is observed among some subdwarfs bluer than this colour. The Ca II K
emission profile in most subdwarfs exhibits an asymmetry of V/R > 1, similar to
that seen in the integrated light of the solar disk. Two quantitative
indicators of the contrast between the peaks in the emission profile and the
neighbouring photospheric line profile are introduced. Measurements of these
indicators show that the level of Ca II emission among the subdwarfs is similar
to that among low-activity Population I dwarfs.

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The categories of this paper are: math
12
The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: q-alg