Discovery of water vapour in the carbon star V Cygni from observations with Herschel/HIFI
Artikel i vetenskaplig tidskrift, 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.

giant branch stars

emission

stars: AGB and post-AGB

chemistry

submillimeter: stars

circumstellar matter

submillimeter

irc+10216

circumstellar envelopes

Författare

D. A. Neufeld

Johns Hopkins University

E. Gonzalez-Alfonso

Universidad de Alcala

G. J. Melnick

Harvard-Smithsonian Center for Astrophysics

M. Pulecka

Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences

M. Schmidt

Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences

R. Szczerba

Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences

V. Bujarrabal

J. Alcolea

J. Cernicharo

Centro de Astrobiologia (CAB)

L. Decin

KU Leuven

Universiteit Van Amsterdam

C. Dominik

Universiteit Van Amsterdam

Radboud Universiteit

Kay Justtanont

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

A. de Koter

Universiteit Van Amsterdam

Sterrekundig Instituut Utrecht

A. P. Marston

European Space Astronomy Centre (ESA)

K. Menten

Max Planck-institutet

Hans Olofsson

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

P. Planesas

Atacama Large Millimeter-submillimeter Array (ALMA)

Fredrik Schöier

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

D. Teyssier

European Space Astronomy Centre (ESA)

Lbfm Waters

Universiteit Van Amsterdam

KU Leuven

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

Universität zu Köln

R. Schieder

Universität zu Köln

S. Philipp

Max Planck-institutet

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 521 1 Article Number: L5- L5

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/201015080