Collisional dust avalanches in debris discs

Grigorieva, Anna; Artymowicz, Pawel; Thébault, P.

doi:10.1051/0004-6361:20065210

Cited by 73 publications

(105 citation statements)

References 44 publications

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“…In approach A, particles in close spatial proximity and with similar velocity vectors are grouped into so-called super-particles (Grigorieva et al 2007), which can be viewed as more or less coherent clouds of particles that move in parallel. When two clouds collide, collision rates among individual particles are calculated based on the local particle-in-a-box principle.…”

Section: Collisional Modelmentioning

confidence: 99%

“…When two clouds collide, collision rates among individual particles are calculated based on the local particle-in-a-box principle. The collision crosssection -or the volume of interaction -of the super-particles can either be defined as a co-moving sphere (e. g., Grigorieva et al 2007) or a (revolving) grid element in polar coordinates (e. g. Kral et al 2013). Smaller interaction volumes reduce the rate of collisions per super-particle, but increase the rate of individual collisions per super-collision.…”

Section: Collisional Modelmentioning

confidence: 99%

“…Smaller super-particles allow for higher spatial (and temporal) resolution, but require more super-particles to reduce noise artefacts. The biggest advantage of this approach is the ability to model short-term effects, such as collisional avalanches (Grigorieva et al 2007), major break-ups of planetesimals (Kral et al 2015, with LIDT-DD) or close stellar flybys (Nesvold et al 2017, with SMACK). Due to the underlying N-body integration, additional forces are easily implemented in these codes, including radiation pressure, draginduced spiralling, resonant capture, and scattering.…”

Section: Collisional Modelmentioning

confidence: 99%

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Collisions and drag in debris discs with eccentric parent belts

Löhne

Krivov

Kirchschlager

et al. 2017

A&A

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Context. High-resolution images of circumstellar debris discs reveal off-centred rings that indicate past or ongoing perturbation, possibly caused by secular gravitational interaction with unseen stellar or substellar companions. The purely dynamical aspects of this departure from radial symmetry are well understood. However, the observed dust is subject to additional forces and effects, most notably collisions and drag. Aims. To complement the studies of dynamics, we therefore aim to understand how new asymmetries are created by the addition of collisional evolution and drag forces, and existing ones strengthened or overridden. Methods. We augmented our existing numerical code "Analysis of Collisional Evolution" (ACE) by an azimuthal dimension, the longitude of periapse. A set of fiducial discs with global eccentricities ranging from 0 to 0.4 is evolved over giga-year timescales. Size distribution and spatial variation of dust are analysed and interpreted. The basic impact of belt eccentricity on spectral energy distributions (SEDs) and images is discussed. Results. We find features imposed on characteristic timescales. First, radiation pressure defines size cutoffs that differ between periapse and apoapse, resulting in an asymmetric halo. The differences in size distribution make the observable asymmetry of the halo depend on wavelength. Second, collisional equilibrium prefers smaller grains on the apastron side of the parent belt, reducing the effect of pericentre glow and the overall asymmetry. Third, Poynting-Robertson drag fills the region interior to an eccentric belt such that the apastron side is more tenuous. Interpretation and prediction of the appearance in scattered light is problematic when spatial and size distribution are coupled.

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Section: Collisional Modelmentioning

confidence: 99%

Section: Collisional Modelmentioning

confidence: 99%

Section: Collisional Modelmentioning

confidence: 99%

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Collisions and drag in debris discs with eccentric parent belts

Löhne

Krivov

Kirchschlager

et al. 2017

A&A

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“…A good explanation for the disappearance of the hot dust is lacking. One of the ideas proposed is that the dust was removed in a collisional avalanche, a runaway process wherein the input of large quantities of small grains that get blown out by radiation pressure break-up larger debris on their way out (Grigorieva et al 2007). If so, the previously high levels of excess will return once the population of small dust is replenished in collisions between the bigger debris that was unaffected by the avalanche.…”

Section: Time Variabilitymentioning

confidence: 99%

Insights into Planet Formation from Debris Disks

Wyatt

Jackson

2016

Space Sci Rev

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Giant impacts refer to collisions between two objects each of which is massive enough to be considered at least a planetary embryo. The putative collision suffered by the proto-Earth that created the Moon is a prime example, though most Solar System bodies bear signatures of such collisions. Current planet formation models predict that an epoch of giant impacts may be inevitable, and observations of debris around other stars are providing mounting evidence that giant impacts feature in the evolution of many planetary systems. This chapter reviews giant impacts, focussing on what we can learn about planet formation by studying debris around other stars. Giant impact debris evolves through mutual collisions and dynamical interactions with planets. General aspects of this evolution are outlined, noting the importance of the collision-point geometry. The detectability of the debris is discussed using the example of the Moon-forming impact. Such debris could be detectable around another star up to 10 Myr post-impact, but model uncertainties could reduce detectability to a few 100 yr window. Nevertheless the 3 % of young stars with debris at levels expected during terrestrial planet formation provide valuable constraints on formation models; implications for super-Earth formation are also discussed. Variability recently observed in some bright disks promises to illuminate the evolution during the earliest phases when vapour condensates may be optically thick and acutely affected by the collision-point geometry. The outer reaches of planetary systems may also exhibit signatures of giant impacts, such as the clumpy debris structures seen around some stars.

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“…9 Integrating over true anomaly rather than, e.g., mean anomaly warrants a higher sampling around the periastron, where sublimation rate varies the most. 10 If the radial geometrical optical depth is higher than ∼10 −2 , the disk is subject to dust avalanches (Grigorieva et al 2007). …”

Section: Collisionsmentioning

confidence: 99%

Near-infrared emission from sublimating dust in collisionally active debris disks

Lieshout

Dominik

Kama

et al. 2014

A&A

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Context. Hot exozodiacal dust is thought to be responsible for excess near-infrared (NIR) emission emanating from the innermost parts of some debris disks. The origin of this dust, however, is still a matter of debate. Aims. We test whether hot exozodiacal dust can be supplied from an exterior parent belt by Poynting-Robertson (P-R) drag, paying special attention to the pile-up of dust that occurs owing to the interplay of P-R drag and dust sublimation. Specifically, we investigate whether pile-ups still occur when collisions are taken into account, and if they can explain the observed NIR excess. Methods. We computed the steady-state distribution of dust in the inner disk by solving the continuity equation. First, we derived an analytical solution under a number of simplifying assumptions. Second, we developed a numerical debris disk model that for the first time treats the complex interaction of collisions, P-R drag, and sublimation in a self-consistent way. From the resulting dust distributions, we generated thermal emission spectra and compare these to observed excess NIR fluxes. Results. We confirm that P-R drag always supplies a small amount of dust to the sublimation zone, but find that a fully consistent treatment yields a maximum amount of dust that is about 7 times lower than that given by analytical estimates. The NIR excess due to this material is much less ( < ∼ 10 −3 for A-type stars with parent belts at > ∼ 1 AU) than the values derived from interferometric observations (∼10 −2 ). Pile-up of dust still occurs when collisions are considered, but its effect on the NIR flux is insignificant. Finally, the cross-section in the innermost regions is clearly dominated by barely bound grains.

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Collisional dust avalanches in debris discs

Cited by 73 publications

References 44 publications

Collisions and drag in debris discs with eccentric parent belts

Collisions and drag in debris discs with eccentric parent belts

Insights into Planet Formation from Debris Disks

Near-infrared emission from sublimating dust in collisionally active debris disks

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