Herschel/HIFI observations of IRC+10216: water vapor in the inner envelope of a carbon-rich AGB star

Abstract

We report the results of observations of ten rotational transitions of water vapor toward the carbon-rich AGB (asymptotic giant branch) 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 1.E+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 H2-17O/H2-16O and H2-18O/H2-16O isotopic abundance ratios of ~ 5.E-3 (3 sigma), providing additional constraints on models for the origin of the water vapor in IRC+10216.

Accepted for publication in the Astrophysical Journal Letters

References in corpus (8)

• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216
• Warm water vapour in the sooty outflow from a luminous carbon star
• A high resolution line survey of IRC+10216 with Herschel. First results: Detection of warm silicon dicarbide SiC2
• Photochemistry in the inner layers of clumpy circumstellar envelopes: formation of water in C-rich objects and of C-bearing molecules in O-rich objects
• A spectral line survey in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216
• The distribution of SiO in the circumstellar envelope around IRC+10216
• Water vapor emission from IRC+10216 and other carbon-rich stars: model predictions and prospects for multitransition observations

Cited by in corpus (13)

• Interstellar water chemistry: from laboratory to observations
• The inner wind of IRC+10216 revisited: New exotic chemistry and diagnostic for dust condensation in carbon stars
• Carbon chemistry in Galactic Bulge Planetary Nebulae
• The widespread occurence of water vapor in the circumstellar envelopes of carbon-rich AGB stars: first results from a survey with Herschel/HIFI
• The complex dust formation zone of the AGB star IRC+10216 probed with CARMA 0.25 arcsec angular resolution molecular observations
• The Role of Internal Photons on the Chemistry of the Circumstellar Envelopes of AGB Stars
• Late Stages of Stellar Evolution - Herschel's contributions
• Constraints on the H2O formation mechanism in the wind of carbon-rich AGB stars
• Connecting the evolution of thermally pulsing asymptotic giant branch stars to the chemistry in their circumstellar envelopes -- I. The case of hydrogen cyanide
• Monitor variability of millimeter lines in IRC +10216
• The first results from the Herschel-HIFI mission
• Herschel/HIFI search for H2-17O and H2-18O in IRC+10216: constraints on models for the origin of water vapor
• Radio and IR interferometry of SiO maser stars