Published by
EDP Sciences
EDP Sciences Journals List
Subscriber Authentication Point
Home All issues Volume 390/ 2 Article
Free access
Issue A&A
Volume 390, Number 2, August I 2002
Page(s) 533 - 553
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020603



A&A 390, 533-553 (2002)
DOI: 10.1051/0004-6361:20020603

The carrier of the "30"  $\mu$m emission feature in evolved stars

A simple model using magnesium sulfide
S. Hony1, L. B. F. M. Waters1, 2 and A. G. G. M. Tielens3, 4

1  Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
2  Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium
3  SRON Laboratory for Space Research Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
4  Kapteyn Astronomical Institute PO Box 800, 9700 AV Groningen, The Netherlands

(Received 4 March 2002 / Accepted 16 April 2002 )

Abstract
We present 2-45  $\mu$m spectra of a large sample of carbon-rich evolved stars in order to study the "30"  $\mu$m feature. We find the "30"  $\mu$m feature in a wide range of sources: low mass loss carbon stars, extreme carbon-stars, post-AGB objects and planetary nebulae. We extract the profiles from the sources by using a simple systematic approach to model the continuum. We find large variations in the wavelength and width of the extracted profiles of the "30"  $\mu$m feature. We modelled the whole range of profiles in a simple way by using magnesium sulfide (MgS) dust grains with a MgS grain temperature different from the continuum temperature. The systematic change in peak positions can be explained by cooling of MgS grains as the star evolves off the AGB. In several sources we find that a residual emission excess at ~26  $\mu$m can also be fitted using MgS grains but with a different grains shape distribution. The profiles of the "30"  $\mu$m feature in planetary nebulae are narrower than our simple MgS model predicts. We discuss the possible reasons for this difference. We find a sample of warm carbon-stars with very cold MgS grains. We discuss possible causes for this phenomenon. We find no evidence for rapid destruction of MgS during the planetary nebula phase and conclude that the MgS may survive to be incorporated in the ISM.


Key words: stars: AGB and post-AGB -- stars: carbon -- circumstellar matter -- stars: mass-loss -- planetary nebulae: general -- infrared: stars

Offprint request: S. Hony, hony@astro.uva.nl

SIMBAD Objects



© ESO 2002

What is OpenURL?

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.