1,368 research outputs found
Vertical structure of debris discs
The vertical thickness of debris discs is often used as a measure of these
systems' dynamical excitation and as clues to the presence of hidden massive
perturbers such as planetary embryos. However, this argument could be flawed
because the observed dust should be naturally placed on inclined orbits by the
combined effect of radiation pressure and mutual collisions. We critically
reinvestigate this issue and numerically estimate what the "natural" vertical
thickness of a collisionally evolving disc is, in the absence of any additional
perturbing body. We use a deterministic collisional code, following the
dynamical evolution of a population of indestructible test grains suffering
mutual inelastic impacts. Grain differential sizes as well as the effect of
radiation pressure are taken into account. We find that, under the coupled
effect of radiation pressure and collisions, grains naturally acquire
inclinations of a few degrees. The disc is stratified with respect to grain
sizes, with the smallest grains having the largest vertical dispersion and the
bigger ones clustered closer to the midplane. Debris discs should have a
minimum "natural" observed aspect ratio at visible to
mid-IR wavelengths where the flux is dominated by the smallest bound grains.
These values are comparable to the estimated thicknesses of many vertically
resolved debris discs, as is illustrated with the specific example of AU Mic.
For all systems with , the presence (or absence) of embedded
perturbing bodies cannot be inferred from the vertical dispersion of the discComment: accepted for publication in Astronomy and Astrophysics (full abstract
in the pdf file
Discovery of extreme asymmetry in the debris disk surrounding HD 15115
We report the first scattered light detection of a dusty debris disk
surrounding the F2V star HD 15115 using the Hubble Space Telescope in the
optical, and Keck adaptive optics in the near-infrared. The most remarkable
property of the HD 15115 disk relative to other debris disks is its extreme
length asymmetry. The east side of the disk is detected to ~315 AU radius,
whereas the west side of the disk has radius >550 AU. We find a blue optical to
near-infrared scattered light color relative to the star that indicates grain
scattering properties similar to the AU Mic debris disk. The existence of a
large debris disk surrounding HD 15115 adds further evidence for membership in
the Beta Pic moving group, which was previously argued based on kinematics
alone. Here we hypothesize that the extreme disk asymmetry is due to dynamical
perturbations from HIP 12545, an M star 0.5 degrees (0.38 pc) east of HD 15115
that shares a common proper motion vector, heliocentric distance, galactic
space velocity, and age.Comment: 4 pages, 3 figures, ApJ Letters, accepte
Feasibility of transit photometry of nearby debris discs
Dust in debris discs is constantly replenished by collisions between larger
objects. In this paper, we investigate a method to detect these collisions. We
generate models based on recent results on the Fomalhaut debris disc, where we
simulate a background star transiting behind the disc, due to the proper motion
of Fomalhaut. By simulating the expanding dust clouds caused by the collisions
in the debris disc, we investigate whether it is possible to observe changes in
the brightness of the background star. We conclude that in the case of the
Fomalhaut debris disc, changes in the optical depth can be observed, with
values of the optical depth ranging from for the densest dust
clouds to for the most diffuse clouds with respect to the background
optical depth of .Comment: 19 pages, 15 figures, accepted for publication in MNRA
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