Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Structured Chromosphere and Wind of TW Hya   A continuous set of echelle spectra of TW Hya, taken with the MIKE
spectrograph on the Magellan2/Clay telescope at Las Campanas Observatory in
April 2006 reveals systematic variations in the flux, velocity, and profile of
the H-alpha emission line which appear to be consistent with the photometric
period of 2.8 days. Absorption features recur at high outflow velocities in the
wind. This behavior suggests that: (a) accretion is not uniformly distributed
over the stellar hemisphere in view; (b) stable structures are present in the
chromosphere, most likely due to the stellar magnetic field configuration.
Semi-empirical models of the atmosphere are constructed to reproduce line
profiles of H-alpha and He I, 10830A and to define the wind structure. These
preliminary calculations suggest the mass loss rate is variable and comparable
to H-alpha mass accretion rates in the literature, requiring a very efficient
mechanism if the wind is powered only by accretion.

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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
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The categories of this paper are: quant-ph
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The categories of this paper are: math
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The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex