Discovery of water vapour in the carbon star V Cygni from observations with Herschel/HIFI
Journal article, 2010
We report the discovery of water vapour toward the carbon star V Cygni. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 1(11)-0(00) para-water transition at 1113.3430 GHz in the upper sideband of the Band 4b receiver. The observed spectral line profile is nearly parabolic, but with a slight asymmetry associated with blueshifted absorption, and the integrated antenna temperature is 1.69 +/- 0.17 K km s(-1). This detection of thermal water vapour emission, carried out as part of a small survey of water in carbon-rich stars, is only the second such detection toward a carbon-rich AGB star, the first having been obtained by the Submillimeter Wave Astronomy Satellite toward IRC+ 10216. For an assumed ortho-to-para ratio of 3 for water, the observed line intensity implies a water outflow rate similar to 3-6 x 10(-5) Earth masses per year and a water abundance relative to H-2 of similar to 2-5 x 10(-6). This value is a factor of at least 10(4) larger than the expected photospheric abundance in a carbon-rich environment, and - as in IRC+ 10216 - raises the intriguing possibility that the observed water is produced by the vapourisation of orbiting comets or dwarf planets. However, observations of the single line observed to date do not permit us to place strong constraints upon the spatial distribution or origin of the observed water, but future observations of additional transitions will allow us to determine the inner radius of the H2O-emitting zone, and the H2O ortho-to-para ratio, and thereby to place important constraints upon the origin of the observed water emission.
irc+10216
chemistry
circumstellar envelopes
giant branch stars
submillimeter
stars: AGB and post-AGB
circumstellar matter
submillimeter: stars
emission
Author
D. A. Neufeld
Johns Hopkins University
E. Gonzalez-Alfonso
University of Alcalá
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
M. Pulecka
Polish Academy of Sciences
M. Schmidt
Polish Academy of Sciences
R. Szczerba
Polish Academy of Sciences
V. Bujarrabal
J. Alcolea
J. Cernicharo
Centro de Astrobiologia (CAB)
L. Decin
KU Leuven
University of Amsterdam
C. Dominik
University of Amsterdam
Radboud University
Kay Justtanont
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
A. de Koter
Sterrekundig Instituut Utrecht
University of Amsterdam
A. P. Marston
European Space Agency (ESA)
K. Menten
Max Planck Society
Hans Olofsson
Chalmers, Earth and Space Sciences, Onsala Space Observatory
P. Planesas
Atacama Large Millimeter-submillimeter Array (ALMA)
Fredrik Schöier
Chalmers, Earth and Space Sciences, Onsala Space Observatory
D. Teyssier
European Space Agency (ESA)
Lbfm Waters
KU Leuven
University of Amsterdam
K. Edwards
University of Waterloo
C. McCoey
University of Waterloo
R. Shipman
Netherlands Institute for Space Research (SRON)
W. Jellema
Netherlands Institute for Space Research (SRON)
T. de Graauw
Atacama Large Millimeter-submillimeter Array (ALMA)
V. Ossenkopf
University of Cologne
R. Schieder
University of Cologne
S. Philipp
Max Planck Society
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L5- L5Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201015080