A HIFI preview of warm molecular gas around chi Cygni: first detection of H2O emission toward an S-type AGB star
Artikel i vetenskaplig tidskrift, 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.
iso-sws
stars: late-type
carbon stars
mass-loss rates
evolved stars
stars: kinematics and
co
stars: mass-loss
dynamics
stars: AGB and post-AGB
circumstellar matter
giant branch stars
circumstellar water-vapor
stars: individual: chi Cyg
w-hydrae
rotational line-profiles
loss history
Författare
Kay Justtanont
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
L. Decin
KU Leuven
Universiteit Van Amsterdam
Fredrik Schöier
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
Matthias Maercker
European Southern Observatory (ESO)
Universität Bonn
Hans Olofsson
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
V. Bujarrabal
Observatorio Astronómico Nacional (OAN)
A. P. Marston
Europeiska rymdorganisationen (ESA)
D. Teyssier
Europeiska rymdorganisationen (ESA)
J. Alcolea
Observatorio Astronómico Nacional (OAN)
J. Cernicharo
Centro de Astrobiologia (CAB)
C. Dominik
Radboud Universiteit
Universiteit Van Amsterdam
A. de Koter
Universiteit Van Amsterdam
Sterrekundig Instituut Utrecht
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
K. Menten
Max-Planck-Gesellschaft
D. A. Neufeld
Johns Hopkins University
P. Planesas
Atacama Large Millimeter-submillimeter Array (ALMA)
Europeiska rymdorganisationen (ESA)
M. Schmidt
Observatorio Astronómico Nacional (OAN)
R. Szczerba
Atacama Large Millimeter-submillimeter Array (ALMA)
R. Waters
KU Leuven
Universiteit Van 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
Universität zu Köln
F. Schmulling
Universität zu Köln
V. Ossenkopf
Universität zu Köln
R. Lai
Northrop Grumman corporation
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L6- L6Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201015092