Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-11-26
Mon.Not.Roy.Astron.Soc. 348 (2004) 1282
Astronomy and Astrophysics
Astrophysics
15 pages, 15 figures, accepted by MNRAS. Revised Eps Eri modelling to show larger range of minimum size cutoffs with porous gr
Scientific paper
10.1111/j.1365-2966.2004.07448.x
We present new sub-mm observations and modelling of Vega excess stars, using realistic dust grain models. For resolved disks, we find that different objects require very different dust grain properties in order to simultaneously fit the image data and SED. Fomalhaut and Vega require solid dust grains, whilst HR4796 and HD141569 can only be fitted using porous grains. The older stars tend to have less porous grains than younger stars, which may indicate that collisions have compacted the dust grains. Eps Eri appears to be deficient in small dust grains compared to our best fitting model. This may be due to factors which affect the size distribution of grains close to the radiation pressure blowout limit. Alternatively, this discrepancy may be due to some external influence on the disk (e.g. a planet). When the model is applied to unresolved targets, an estimate of the disk size can be made. However, the large diversity in dust composition for the resolved disks means that we cannot make a reliable assumption as to the composition of the grains in an unresolved disk, and there is corresponding uncertainty in the disk size. In addition, the poor fit for Eps Eri shows that the model cannot always account for the SED even if the disk size is known. These two factors mean that it may not be possible to determine a disk's size without actually resolving it.
Dent William R. F.
Sheret I.
Wyatt Mark C.
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