Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005jrasc..99q.135c&link_type=abstract
Journal of the Royal Astronomical Society of Canada, Vol. 99, No. 4, p.135
Astronomy and Astrophysics
Astronomy
Scientific paper
Asymmetries are routinely observed in circumstellar dust disks, such as those seen at beta Pictoris, epsilon Eridani, AU Microscopii, HD107146, etc.Two broad categories of phenomenon are often invoked to explain these asymmetries: asymmetric scattering of starlight by dust (due to forward scattering, which makes the near side of an inclined disk appear brighter than the far side) and planetary perturbations (which can organize the dust orbits in nested, elliptical streamlines). Furthermore, the nature of a dusty disk's asymmetric appearance is wavelength dependent. When viewed via the disk's thermal emission, stellar heating of dust near periapse leads to the pericentre glow feature seen in images of dust-disks (Wyatt et al. 1999). However maps of reflected starlight of a disk reveal an apocentre enhancement, due to dust loitering near apoapse (Marsh et al. 2005, astro-ph/0501140). The aim of this work is to address these two broad categories, and to illustrate how it is possible to distinguish their effects in the appearance of a circumstellar dust-disk. To model the effects of planetary perturbations, we consider for now only singleplanet systems, and we neglect the effects of radiation forces on the dust. We also assume that the planet's secular perturbations are the dominant disturbance in the disk. To account for the disk's asymmetric scattering of starlight, we use a Henyey-Greenstein function to describe the phase function for dust grains. Using this simple model, a disk's asymmetry is governed by just three parameters: the planet's eccentricity (e), the disk's inclination (i), and the light-scattering parameter (g). Comparison of synthetic optical-depth maps of dusty disks generated using our models can then be used to discriminate between these two competing phenomenon. We will also present a simple analytic expression that relates the disk's surface brightness profile to e, i, and g, and will also present preliminary results for our analysis of the beta Pictoris system.
Capobianco Christopher C.
Hahn Joseph M.
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