A&A 413, 241-249 (2004)
DOI: 10.1051/0004-6361:20031487

Australia Telescope Compact Array imaging of circumstellar HCN line emission from R Scl

T. Wong¹, F. L. Schöier^{2, 3}, M. Lindqvist⁴ and H. Olofsson<sup>3

1</sup>  CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia
²  Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
³  Stockholm Observatory, AlbaNova, 106 91 Stockholm, Sweden
⁴  Onsala Space Observatory, 439 92 Onsala, Sweden

(Received 9 May 2003 / Accepted 19 September 2003 )

Abstract
We present radio-interferometric observations of HCN line emission from the carbon star R Scl, obtained with the interim 3-mm receivers of the Australia Telescope Compact Array. The emission is resolved into a central source with a Gaussian FWHM of ~1´´, which we identify as the present mass loss envelope. Using a simple photodissociation model and constraints from single-dish HCN spectra, we argue that the present mass-loss rate is low,  yr ^-1, supporting the idea that R Scl had to experience a brief episode of intense mass loss in order to produce the detached CO shell at ~10´´ radius inferred from single-dish observations. Detailed radiative transfer modelling yields an abundance of HCN relative to H ₂,  f_HCN, of  in the present-day wind. There appears to be a discrepancy between model results obtained with higher transition single-dish data included and those from the interferometer data alone, in that the interferometer data suggest a smaller envelope size and larger HCN abundance than the single-dish data. The lack of HCN in the detached shell, , is consistent with the rapid photodissociation of HCN into CN as it expands away from the star.

Key words: circumstellar matter -- stars: carbon -- stars: AGB and post-AGB -- stars: mass-loss

Offprint request: T. Wong, Tony.Wong@csiro.au

SIMBAD Objects

© ESO 2004

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

• If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
• You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
• You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.