TY  - JOUR
AU  - Justtanont, K.
AU  - Decin, L.
AU  - Schöier, F. L.
AU  - Maercker, M.
AU  - Olofsson, H.
AU  - Bujarrabal, V.
AU  - Marston, A. P.
AU  - Teyssier, D.
AU  - Alcolea, J.
AU  - Cernicharo, J.
AU  - Dominik, C.
AU  - de Koter, A.
AU  - Melnick, G.
AU  - Menten, K.
AU  - Neufeld, D.
AU  - Planesas, P.
AU  - Schmidt, M.
AU  - Szczerba, R.
AU  - Waters, R.
AU  - de Graauw, Th
AU  - Whyborn, N.
AU  - Finn, T.
AU  - Helmich, F.
AU  - Siebertz, O.
AU  - Schmülling, F.
AU  - Ossenkopf, V.
AU  - Lai, R.
PY  - 2010
DA  - 2010//
TI  - A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-type AGB star
JO  - Astron. Astrophys.
SP  - L6
VL  - 521
KW  - HEB mixer applications
KW  - HIFI
KW  - Herschel
KW  - stars: AGB and post-AGB / circumstellar matter / stars: kinematics and dynamics / stars: individual: χ Cyg / stars: late-type / stars: mass-loss
AB  - Aims. A set of new, sensitive, and spectrally resolved, sub-millimeter line observations are used to probe the warm circumstellar gas around the S-type AGB star χ Cyg. The observed lines involve high rotational quantum numbers, which, combined with previously obtained lower-frequency data, make it possible to study in detail the chemical and physical properties of, essentially, the entire circumstellar envelope of χ Cyg.Methods. The data were obtained using the HIFI instrument aboard Herschel, whose high spectral resolution provides valuable information about the line profiles. Detailed, non-LTE, radiative transfer modelling, including dust radiative transfer coupled with a dynamical model, has been performed to derive the temperature, density, and velocity structure of the circumstellar envelope.Results. We report the first detection of circumstellar H2O rotational emission lines in an S-star. Using the high-J CO lines to derive the parameters for the circumstellar envelope, we modelled both the ortho- and para-H2O lines. Our modelling results are consistent with the velocity structure expected for a dust-driven wind. The derived total H2O abundance (relative to H2) is (1.1±0.2) × 10-5, much lower than that in O-rich stars. The derived ortho-to-para ratio of 2.1±0.6 is close to the high-temperature equilibrium limit, consistent with H2O being formed in the photosphere.
UR  - https://doi.org/10.1051/0004-6361/201015092
DO  - 10.1051/0004-6361/201015092
N1  - exported from refbase (https://db.rplab.ru/refbase/show.php?record=1096), last updated on Fri, 17 Jun 2016 17:12:56 -0500
ID  - Justtanont_etal2010
ER  -