Radiative transfer in dust clouds. IV. Circumstellar dust shells around carbon stars.
Abstract
The solution of the equation of radiative transfer developed by Rowan-Robinson is applied to a sample of 41 carbon stars and three others displaying similar characteristics. All of these have appreciable infrared excesses. The models, consisting of a star in a spherically symmetric circumstellar dust shell (CDS), are compared with the available observational data. All the CDS can be successfully modelled with an n(r)∝r-2 density distribution, consistent with steady outflow at a constant velocity. Amorphous carbon-type grains, having a QV∝V absorption efficiency, are found to model the sources with considerably more success than graphite grains, though it has also proved necessary to modify this somewhat at wavelengths λ ≲ 1.4μm in order to fit the shortest wavelength data where available. We adopt TS (temperature of central blackbody source) = 2500 K for stars of types C4 - C6 and 2000 K for C7 - C9.
In particular we compare our model of IRC + 10216 with the available infrared size measurements and with the models of other authors.- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 1983
- DOI:
- 10.1093/mnras/202.3.797
- Bibcode:
- 1983MNRAS.202..797R