HERSCHEL /HIFI OBSERVATIONS OF IRC+10216: WATER VAPOR IN THE INNER ENVELOPE OF A CARBON-RICH ASYMPTOTIC GIANT BRANCH STAR
- Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
- Departamento de Fisica, Universidad de Alcala de Henares, Campus Universitario, E-28871 Alcala de Henares, Madrid (Spain)
- Harvard-Smithsonian CfA, Cambridge, MA 02138 (United States)
- N. Copernicus Astronomical Center, Torun (Poland)
- Instituut voor Sterrenkunde, K. U. Leuven (Belgium)
- Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, NL-1098 Amsterdam (Netherlands)
- Onsala Space Observatory, Department of Radio and Space Science, Chalmers University of Technology, SE-43992 Onsala (Sweden)
- CAB, INTA-CSIC, Ctra de Torrejon a Ajalvir, Madrid (Spain)
We report the results of observations of 10 rotational transitions of water vapor toward the carbon-rich asymptotic giant branch (AGB) star IRC+10216 (CW Leonis), carried out with Herschel's HIFI instrument. Each transition was securely detected by means of observations using the dual beam switch mode of HIFI. The measured line ratios imply that water vapor is present in the inner outflow at small distances ({<=}few x 10{sup 14} cm) from the star, confirming recent results reported by Decin et al. from observations with Herschel's PACS and SPIRE instruments. This finding definitively rules out the hypothesis that the observed water results from the vaporization of small icy objects in circular orbits. The origin of water within the dense C-rich envelope of IRC+10216 remains poorly understood. We derive upper limits on the H{sup 17}{sub 2}O/H{sup 16}{sub 2}O and H{sup 18}{sub 2}O/H{sup 16}{sub 2}O isotopic abundance ratios of {approx}5 x 10{sup -3} (3{sigma}), providing additional constraints on models for the origin of the water vapor in IRC+10216.
- OSTI ID:
- 21560545
- Journal Information:
- Astrophysical Journal Letters, Vol. 727, Issue 2; Other Information: DOI: 10.1088/2041-8205/727/2/L28; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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