Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aas...212.1709p&link_type=abstract
American Astronomical Society, AAS Meeting #212, #17.09; Bulletin of the American Astronomical Society, Vol. 40, p.531
Astronomy and Astrophysics
Astronomy
Scientific paper
Massive circumstellar envelopes of Asymptotic Giant Branch (AGB) stars are believed to be one of the main contributors of molecules and grains to the interstellar medium. IRC+10216 is a well known archetype of an AGB carbon star with a high mass-loss rate. Due to its close proximity ( 150 pc), this star is an ideal target for detailed studies of physical and chemical processes in AGB circumstellar envelopes.
Using the Submillimeter Array (SMA), we have begun the first interferometric spectral line-survey of IRC+10216 in the 345 GHz band. We have found a large sample of molecular emission lines with narrow line-widths implying expansion velocities of 4 km/s (in contrast with the typical value of the expansion velocity of 14.5 km/s known from previous surveys). The emission from these narrow lines is spatially unresolved with our 3"x2" synthesized beam in SMA's subcompact configuration. We present here results on some of these lines which have been identified as vibrationally excited transition of Si34S, 29SiS, CS and CO. All these are new detections toward IRC+10216. The CO v=1 J=3-2 line is tentatively identified. If confirmed, it will be the first astronomical detection of vibrationally excited CO.
We also present results from SMA extended array observations with higher angular resolution (0.8"x0.6") of 29SiS and CS lines. The emission continues to remain unresolved, implying that the narrow-line emission is coming from the region close to the star (within 60 AU), where the stellar wind is still being accelerated. We plan to carry out higher angular resolution observations with the very extended configuration of the SMA at an angular resolution of 0.3". These observations will probably allow us to probe physical conditions and kinematics in the region where dust is forming.
Bruenken Sandra
Gottleib C. A.
Hedden Abigail S.
McCarthy Mary C.
Menten Karl. M.
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