Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Herschel/HIFI observations of high-J CO transitions in the
  protoplanetary nebula CRL618   We performed Herschel/HIFI observations of several CO lines in the
far-infrared/sub-mm in the protoplanetary nebula CRL618. The high spectral
resolution provided by HIFI allows measurement of the line profiles. Since the
dynamics and structure of the nebula is well known from mm-wave interferometric
maps, it is possible to identify the contributions of the different nebular
components (fast bipolar outflows, double shells, compact slow shell) to the
line profiles. The observation of these relatively high-energy transitions
allows an accurate study of the excitation conditions in these components,
particularly in the warm ones, which cannot be properly studied from the
low-energy lines.
  The 12CO J=16-15, 10-9, and 6-5 lines are easily detected in this source.
13CO J=10-9 and 6-5 are also detected. Wide profiles showing spectacular line
wings have been found, particularly in 12CO 16-15. Other lines observed
simultaneously with CO are also shown. Our analysis of the CO high-J
transitions, when compared with the existing models, confirms the very low
expansion velocity of the central, dense component, which probably indicates
that the shells ejected during the last AGB phases were driven by radiation
pressure under a regime of maximum transfer of momentum. No contribution of the
diffuse halo found from mm-wave data is identified in our spectra, because of
its low temperature. We find that the fast bipolar outflow is quite hot, much
hotter than previously estimated; for instance, gas flowing at 100 km/s must
have a temperature higher than ~ 200 K. Probably, this very fast outflow, with
a kinematic age < 100 yr, has been accelerated by a shock and has not yet
cooled down. The double empty shell found from mm-wave mapping must also be
relatively hot, in agreement with the previous estimate.

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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat