A HIFI preview of warm molecular gas around chi Cygni: first detection of H2O emission toward an S-type AGB star
Journal article, 2010
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 chi Cyg. The observed lines involve high rotational quantum numbers, which, combined with previously obtained lower-frequency data, make it posible to study in detail the chemical and physical properties of, essentially, the entire circumstellar envelope of chi 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 H-2) is (1.1 +/- 0.2) x 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.
loss history
circumstellar water-vapor
stars: AGB and post-AGB
circumstellar matter
evolved stars
iso-sws
w-hydrae
rotational line-profiles
carbon stars
giant branch stars
stars: individual: chi Cyg
stars: late-type
dynamics
co
stars: mass-loss
stars: kinematics and
mass-loss rates
Author
Kay Justtanont
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
L. Decin
KU Leuven
University of Amsterdam
Fredrik Schöier
Chalmers, Earth and Space Sciences, Onsala Space Observatory
Matthias Maercker
University of Bonn
European Southern Observatory (ESO)
Hans Olofsson
Chalmers, Earth and Space Sciences, Onsala Space Observatory
V. Bujarrabal
Spanish National Observatory (OAN)
A. P. Marston
European Space Astronomy Centre (ESAC)
D. Teyssier
European Space Astronomy Centre (ESAC)
J. Alcolea
Spanish National Observatory (OAN)
J. Cernicharo
Centro de Astrobiologia (CAB)
C. Dominik
Radboud University
University of Amsterdam
A. de Koter
Sterrekundig Instituut Utrecht
University of Amsterdam
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
K. Menten
Max Planck Society
D. A. Neufeld
Johns Hopkins University
P. Planesas
Atacama Large Millimeter-submillimeter Array (ALMA)
European Space Astronomy Centre (ESAC)
M. Schmidt
Spanish National Observatory (OAN)
R. Szczerba
Atacama Large Millimeter-submillimeter Array (ALMA)
R. Waters
KU Leuven
University of Amsterdam
T. de Graauw
Polish Academy of Sciences
N. Whyborn
Atacama Large Millimeter-submillimeter Array (ALMA)
T. Finn
Maynooth University
F. Helmich
Netherlands Institute for Space Research (SRON)
O. Siebertz
University of Cologne
F. Schmulling
University of Cologne
V. Ossenkopf
University of Cologne
R. Lai
Northrop Grumman corporation
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L6- L6Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201015092