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Author Justtanont, K.; Decin, L.; Schöier, F. L.; Maercker, M.; Olofsson, H.; Bujarrabal, V.; Marston, A. P.; Teyssier, D.; Alcolea, J.; Cernicharo, J.; Dominik, C.; de Koter, A.; Melnick, G.; Menten, K.; Neufeld, D.; Planesas, P.; Schmidt, M.; Szczerba, R.; Waters, R.; de Graauw, Th.; Whyborn, N.; Finn, T.; Helmich, F.; Siebertz, O.; Schmülling, F.; Ossenkopf, V.; Lai, R. doi  openurl
  Title A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-type AGB star Type Journal Article
  Year 2010 Publication Astron. Astrophys. Abbreviated Journal  
  Volume 521 Issue Pages L6  
  Keywords HEB mixer applications, HIFI, Herschel, stars: AGB and post-AGB / circumstellar matter / stars: kinematics and dynamics / stars: individual: χ Cyg / stars: late-type / stars: mass-loss  
  Abstract (down) Aims. A set of new, sensitive, and spectrally resolved, sub-millimeter line observations are used to probe the warm circumstellar gas around the S-type AGB star χ Cyg. The observed lines involve high rotational quantum numbers, which, combined with previously obtained lower-frequency data, make it possible to study in detail the chemical and physical properties of, essentially, the entire circumstellar envelope of χ Cyg.

Methods. The data were obtained using the HIFI instrument aboard Herschel, whose high spectral resolution provides valuable information about the line profiles. Detailed, non-LTE, radiative transfer modelling, including dust radiative transfer coupled with a dynamical model, has been performed to derive the temperature, density, and velocity structure of the circumstellar envelope.

Results. We report the first detection of circumstellar H2O rotational emission lines in an S-star. Using the high-J CO lines to derive the parameters for the circumstellar envelope, we modelled both the ortho- and para-H2O lines. Our modelling results are consistent with the velocity structure expected for a dust-driven wind. The derived total H2O abundance (relative to H2) is (1.1±0.2) × 10-5, much lower than that in O-rich stars. The derived ortho-to-para ratio of 2.1±0.6 is close to the high-temperature equilibrium limit, consistent with H2O being formed in the photosphere.
 
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  Call Number Serial 1096  
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Author de Graauw, T.; Caux, E.; Guesten, R.; Helmich, F.; Pearson, J.; Phillips, T. G.; Schieder, R.; Tielens, X.; Saraceno, P.; Stutzki, J.; Wafelbakker, C. K.; Whyborn, N. D. openurl 
  Title The Herschel-heterodyne instrument for the far-infrared (HIFI) Type Conference Article
  Year 2005 Publication Bulletin of the American Astronomical Society Abbreviated Journal  
  Volume Issue Pages 1219  
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  Language Summary Language Original Title  
  Series Editor Series Title Bulletin of the American Astronomical Society Abbreviated Series Title  
  Series Volume 37 Series Issue Edition  
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  Notes Approved no  
  Call Number ref2005AAS...207.3503D Serial 420  
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Author Wild, W.; de Graauw, Th.; Baryshev, A.; Bos, A.; Gao, J. R.; Gunst, A.; Helmich, F.; ter Horst, R.; Jackson, B.; Maat, P.; Noordam, J.; Roelfsema, P.; Venema, L.; Whyborn, N.; Yagoubov, P. openurl 
  Title Terahertz technology for ESPRIT – a far-infrared space interferometer Type Conference Article
  Year 2005 Publication Proc. 16th Int. Symp. Space Terahertz Technol. Abbreviated Journal  
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  Publisher Place of Publication Göteborg, Sweden Editor  
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  Notes Approved no  
  Call Number RPLAB @ s @ ESPRIT_interferom_Wild Serial 365  
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