EDP Sciences
Free access
Volume 485, Number 3, July III 2008
Page(s) L33 - L36
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200810193
Published online 04 June 2008

A&A 485, L33-L36 (2008)
DOI: 10.1051/0004-6361:200810193


Tentative detection of phosphine in IRC +10216

M. Agúndez1, J. Cernicharo1, J. R. Pardo1, M. Guélin2, and T. G. Phillips3

1  Departamento de Astrofísica Molecular e Infrarroja, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain
    e-mail: [marce;cerni;pardo]@damir.iem.csic.es
2  Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Hères, and LERMA/École Normale Supérieure, 24 rue Lhomond, 75231 Paris, France
    e-mail: guelin@iram.fr
3  California Institute of Technology, Downs Laboratory of Physics 320-47, Pasadena, CA 91125, USA
    e-mail: tgp@submm.caltech.edu

Received 14 May 2008 / Accepted 27 May 2008

Aims. The $J_{\rm K}$ = 10-00 rotational transition of phosphine (PH3) at 267 GHz has been tentatively identified with a $T_{\rm
MB}$ ~ 40 mK spectral line observed with the IRAM 30-m telescope in the C-star envelope IRC +10216.
Methods. A radiative transfer model was used to fit the observed line profile.
Results. The derived PH3 abundance relative to H2 is 6 $\times$ 10-9, although it may have a large uncertainty due to the lack of knowledge about the spatial distribution of this species. If our identification is correct, it implies that PH3 has a similar abundance to what is reported for HCP in this source and that these two molecules (HCP and PH3) together take up about 5% of phosphorus in IRC +10216. The abundance of PH3, like that of other hydrides in this source, is not well explained by conventional gas-phase LTE and non-LTE chemical models, and may imply formation on grain surfaces.

Key words: stars: individual: IRC +10216 -- stars: carbon -- radio lines: stars -- astrochemistry -- line: identification -- stars: AGB and post-AGB

© ESO 2008