Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fluxes in H\alpha and Ca II H and K for a sample of Southern stars   The main chromospheric activity indicator is the S index, which is esentially
the ratio of the flux in the core of the Ca II H and K lines to the continuum
nearby, and is well studied basically for stars from F to K. Another usual
chromospheric proxy is the H\alpha line, which is beleived to be tightly
correlated with the Ca II index. In this work we characterize both
chromospheric activity indicators, one associated with the H and K Ca II lines
and the other with H\alpha, for the whole range of late type stars, from F to
M. We present periodical medium-resolution echelle observations covering the
complete visual range, which were taken at the CASLEO Argentinean Observatory.
These observations are distributed along 7 years. We use a total of 917
flux-calibrated spectra for 109 stars which range from F6 to M5. We
statistically study these two indicators for stars of different activity levels
and spectral types. We directly derive the conversion factor which translate
the known S index to flux in the Ca II cores, and extend its calibration to a
wider spectral range. We investigate the relation between the activity
measurements in the calcium and hydrogen lines, and found that the usual
correlation observed is basically the product of the dependence of each flux
with stellar colour, and not the product of similar activity phenomena.

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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: funct-an
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The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: nlin
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The categories of this paper are: acc-phys
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The categories of this paper are: physics
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn