Summary: Mon. Not. R. Astron. Soc. 000, 000--000 (0000) Printed 19 November 1997 (MN L A T E X style file v1.4)
Observations and modelling of spectral energy
distributions of carbon stars with optically thin envelopes
S. Bagnulo 1 , J.G. Doyle 1 , V. Andretta 1;2
1 Armagh Observatory, College Hill, Armagh BT619DG, N. Ireland. Email: firstname.lastname@example.org & email@example.com
2 Present address: NASA/GSFC, Laboratory for Astronomy and Solar Physics, Code 682, Greenbelt, MD 20771, USA.
We present broadband photometry in the optical, near infrared and submillimetre,
and midinfrared spectrophotometry of a selection of carbon stars with optically thin
envelopes. Most of the observations were carried out simultaneously.
Beside the emission feature at 11:3 Żm due to silicon carbide grains in the circumstellar
environment, many of our midinfrared spectra show an emission feature at 8:6 Żm.
All the observed spectral energy distributions exhibit a very large farinfrared flux
excess. Both these features are indeed common to many carbon stars surrounded by
optically thin envelopes.
We modelled the observed spectral energy distributions by means of a full radiative
transfer treatment, paying a particular attention to the features quoted above. The
peak at 8:6 Żm is usually ascribed to the presence of hydrogenated amorphous carbon