Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Factory and The Beehive II. Activity and Rotation in Praesepe and
  the Hyades   Open clusters are collections of stars with a single, well-determined age,
and can be used to investigate the connections between angular-momentum
evolution and magnetic activity over a star's lifetime. We present the results
of a comparative study of the relationship between stellar rotation and
activity in two benchmark open clusters: Praesepe and the Hyades. As they have
the same age and roughly solar metallicity, these clusters serve as an ideal
laboratory for testing the agreement between theoretical and empirical
rotation-activity relations at $\approx$600 Myr. We have compiled a sample of
720 spectra --- more than half of which are new observations --- for 516
high-confidence members of Praesepe; we have also obtained 139 new spectra for
130 high-confidence Hyads. We have collected rotation periods ($P_{rot}$) for
135 Praesepe members and 87 Hyads. To compare $H\alpha$ emission, an indicator
of chromospheric activity, as a function of color, mass, and Rossby number
$R_o$, we first calculate an expanded set of $\chi$ values, with which we can
obtain the $H\alpha$ to bolometric luminosity ratio, $L_{H\alpha}/L_{bol}$,
even when spectra are not flux-calibrated and/or stars lack reliable distances.
Our $\chi$ values cover a broader range of stellar masses and colors (roughly
equivalent to spectral types from K0 to M9), and exhibit better agreement
between independent calculations, than existing values. We find no difference
between the two clusters in their $H\alpha$ equivalent width or
$L_{H\alpha}/L_{bol}$ distributions, and therefore take the merged $H\alpha$
and $P_{rot}$ data to be representative of 600-Myr-old stars. Our analysis
shows that $H\alpha$ activity in these stars is saturated for
$R_o\leq0.11^{+0.02}_{-0.03}$. Above that value activity declines as a
power-law with slope $\beta=-0.73^{+0.16}_{-0.12}$, before dropping off rapidly
at $R_o\approx0.4$...

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The categories of this paper are: nucl-ex
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The categories of this paper are: physics
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The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph