Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Echelle long-slit optical spectroscopy of evolved stars   We present echelle long-slit optical spectra of a sample of objects evolving
off the AGB, most of them in the pre-planetary nebula (pPN) phase, obtained
with the ESI and MIKE spectrographs at Keck-II and Magellan-I, respectively.
The total wavelength range covered with ESI (MIKE) is ~3900 to 10900 A (~3600
to 7200A). In this paper, we focus our analysis mainly on the Halpha profiles.
Prominent Halpha emission is detected in half of the objects, most of which
show broad Halpha wings (up to ~4000 km/s). In the majority of the
Halpha-emission sources, fast, post-AGB winds are revealed by P-Cygni profiles.
In ~37% of the objects Halpha is observed in absorption. In almost all cases,
the absorption profile is partially filled with emission, leading to complex,
structured profiles that are interpreted as an indication of incipient post-AGB
mass-loss. All sources in which Halpha is seen mainly in absorption have F-G
type central stars, whereas sources with intense Halpha emission span a larger
range of spectral types from O to G. Shocks may be an important excitation
agent of the close stellar surroundings for objects with late type central
stars. Sources with pure emission or P Cygni Halpha profiles have larger J-K
color excess than objects with Halpha mainly in absorption, which suggests the
presence of warm dust near the star in the former. The two classes of profile
sources also segregate in the IRAS color-color diagram in a way that intense
Halpha-emitters have dust grains with a larger range of temperatures.
(abridged)

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The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio
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The categories of this paper are: stat
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The categories of this paper are: eess
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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: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: econ