NEUFELD, David A.; TOLLS, Volker; AGÚNDEZ, M.; GONZÁLEZ-ALFONSO, Eduardo; DECIN, Leen; DANIEL, Fabien; CERNICHARO, José; MELNICK, Gary J.; SCHMIDT, Miroslaw; SZCZERBA, Ryszard

doi:10.1088/2041-8205/767/1/L3

Métadonnées

Afficher la notice complète

Licence d’utilisation du document

NEUFELD, David A.

TOLLS, Volker

AGÚNDEZ, M.
SSE 2013

Langue

Article de revue

Ce document a été publié dans

The Astrophysical journal letters. 2013, vol. 767, n° 1, p. id. L3

Bristol : IOP Publishing

Résumé en anglais

We report the results of a sensitive search for the minor isotopologues of water, H2-17O and H2-18O, toward the carbon-rich AGB star IRC+10216 (a.k.a. CW Leonis) using the HIFI instrument on the Herschel Space Observatory. This search was motivated by the fact that any detection of isotopic enhancement in the H2-17O and H2-18O abundances would have strongly implicated CO photodissociation as the source of the atomic oxygen needed to produce water in a carbon-rich circumstellar envelope. Our observations place an upper limit of 1/470 on the H2-17O/H2-16O abundance ratio. Given the isotopic 17O/16O ratio of 1/840 inferred previously for the photosphere of IRC+10216, this result places an upper limit of a factor 1.8 on the extent of any isotope-selective enhancement of H2-17O in the circumstellar material, and provides an important constraint on any model that invokes CO photodissociation as the source of O for H2O production. In the context of the clumpy photodissociation model proposed previously for the origin of water in IRC+10216, our limit implies that 12C-16O (not 13C-16O or SiO) must be the dominant source of 16O for H2O production, and that the effects of self-shielding can only have reduced the 12C-16O photodissociation rate by at most a factor ~ 2.< Réduire

Métadonnées

Licence d’utilisation du document

Herschel/HIFI search for H2-17O and H2-18O in IRC+10216: constraints on models for the origin of water vapor

Langue

Ce document a été publié dans

Résumé en anglais

DOI

Origine

Unités de recherche