SIMBAD references

We utilise a modelling technique in which a generalised two-stream Eddington approximation is applied to the problem of the radiative transfer in a spherically symmetric dust shell. We calculate the emerging flux taking into account the effect of non-isotropic scattering, absorption and thermal reemission for a multiple grain size, multiple grain component distribution. We have applied our technique to the well known carbon-rich star IRC +10 216; we have considered a model with grains of amorphous carbon and silicon carbide, and we have studied how different grain size distributions affect the transport coefficients and the calculated flux. In agreement with previous works, we reproduce quite well the general spectral characteristics, spanning from λ=0.55µm to 2cm, assuming the dust envelope composed of small grains (with radius ∼10^–2µm) of amorphous carbons. The presence of silicon carbide cannot be excluded, but it is not required to explain the feature at 11.4µm observed in the IRAS Low Resolution Spectrum: a one-component model including only amorphous carbons fits both the general characteristics and the feature at 11.4µm