scholarly journals Twisted debris: how differential secular perturbations shape debris disks

2019 ◽  
Vol 631 ◽  
pp. A141
Author(s):  
J. A. Sende ◽  
T. Löhne
Keyword(s):  
Debris Disks ◽  
Orbital Elements ◽  
Secular Perturbations ◽  
Asymmetric Structures ◽  
Analytic Approximations ◽  
Grain Sizes ◽  
Gravitational Perturbations ◽  
Small Grains ◽  
Basic Equations ◽  
Collisional Evolution

Context. Resolved images suggest that asymmetric structures are a common feature of cold debris disks. While planets close to these disks are rarely detected, their hidden presence and gravitational perturbations provide plausible explanations for some of these features. Aims. To put constraints on the properties of yet undetected planetary companions, we aim to predict what features such a planet imprints in debris disks undergoing continuous collisional evolution. Methods. We discuss the basic equations, analytic approximations and timescales governing collisions, radiation pressure and secular perturbations. In addition, we combine our numerical model of the collisional evolution of the size and spatial distributions in debris disks with the gravitational perturbation by a single planet. Results. We find that the distributions of orbital elements in the disks are strongly dependent on grain sizes. Secular precession is differential with respect to involved semi-major axes and grain sizes. This leads to observable differences between the big grains tracing the parent belt and the small grains in the trailing halo. Observations at different wavelengths can be used to constrain the properties of a possible planet.

scholarly journals Configuration of the Martian dust rings: shapes, densities, and size distributions from direct integrations of particle trajectories

2020 ◽  
Vol 500 (3) ◽  
pp. 2979-2985
Author(s):  
Xiaodong Liu ◽  
Jürgen Schmidt
Keyword(s):  
Size Range ◽  
Solar Radiation Pressure ◽  
Dust Particles ◽  
Size Distributions ◽  
Grain Sizes ◽  
Gravitational Perturbations ◽  
Ring Configuration ◽  
Upper Limits ◽  
Configuration Simulation ◽  
Fifth Order

ABSTRACT It is expected since the early 1970s that tenuous dust rings are formed by grains ejected from the Martian moons Phobos and Deimos by impacts of hypervelocity interplanetary projectiles. In this paper, we perform direct numerical integrations of a large number of dust particles originating from Phobos and Deimos. In the numerical simulations, the most relevant forces acting on the dust are included: Martian gravity with spherical harmonics up to fifth degree and fifth order, gravitational perturbations from the Sun, Phobos, and Deimos, solar radiation pressure, as well as the Poynting–Robertson drag. In order to obtain the ring configuration, simulation results of various grain sizes ranging from submicrometres to 100 μm are averaged over a specified initial mass distribution of ejecta. We find that for the Phobos ring grains smaller than about 2 μm are dominant; while the Deimos ring is dominated by dust in the size range of about 5–20 μm. The asymmetries, number densities, and geometric optical depths of the rings are quantified from simulations. The results are compared with the upper limits of the optical depth inferred from Hubble observations. We compare to previous work and discuss the uncertainties of the models.

scholarly journals Nautilus multi-grain model: Importance of cosmic-ray-induced desorption in determining the chemical abundances in the ISM

2018 ◽  
Vol 615 ◽  
pp. A20 ◽  
Author(s):  
Wasim Iqbal ◽  
Valentine Wakelam
Keyword(s):  
Grain Size ◽  
Surface Temperature ◽  
Gas Phase ◽  
Numerical Models ◽  
Cosmic Ray ◽  
Grain Sizes ◽  
Small Grains ◽  
Grain Model ◽  
Grain Surface ◽  
The Impact

Context. Species abundances in the interstellar medium (ISM) strongly depend on the chemistry occurring at the surfaces of the dust grains. To describe the complexity of the chemistry, various numerical models have been constructed. In most of these models, the grains are described by a single size of 0.1 μm. Aims. We study the impact on the abundances of many species observed in the cold cores by considering several grain sizes in the Nautilus multi-grain model. Methods. We used grain sizes with radii in the range of 0.005 μm to 0.25 μm. We sampled this range in many bins. We used the previously published, MRN and WD grain size distributions to calculate the number density of grains in each bin. Other parameters such as the grain surface temperature or the cosmic-ray-induced desorption rates also vary with grain sizes. Results. We present the abundances of various molecules in the gas phase and also on the dust surface at different time intervals during the simulation. We present a comparative study of results obtained using the single grain and the multi-grain models. We also compare our results with the observed abundances in TMC-1 and L134N clouds. Conclusions. We show that the grain size, the grain size dependent surface temperature and the peak surface temperature induced by cosmic ray collisions, play key roles in determining the ice and the gas phase abundances of various molecules. We also show that the differences between the MRN and the WD models are crucial for better fitting the observed abundances in different regions in the ISM. We show that the small grains play a very important role in the enrichment of the gas phase with the species which are mainly formed on the grain surface, as non-thermal desorption induced by collisions of cosmic ray particles is very efficient on the small grains.

scholarly journals A New Approach to Evaluate Planetary Perturbations on a Cloud of Dust in Low Eccentricity Heliocentric Orbits

1985 ◽  
Vol 85 ◽  
pp. 381-384 ◽  
Author(s):  
Bo. Å. S. Gustafson
Keyword(s):  
Dust Cloud ◽  
Frame Of Reference ◽  
Orbital Elements ◽  
New Approach ◽  
Gravitational Perturbations ◽  
Time Integral ◽  
Common Coordinate System ◽  
Heliocentric Orbits ◽  
Single Matrix ◽  
Over Time

AbstractDynamical perturbations on ensembles of particles in heliocentric orbits of low eccentricity are integrated over time. The dust is perturbed by radiation pressure, Poynting-Robertson drag, their corpuscular counterparts, and by gravitation due to any number of planets. A dust cloud is represented by a set of centroids and orbital dispersions (about the centroids). Gravitational perturbations on the centroid are derived from a single matrix, valid for any planet, in the appropriate frame of reference. After transformation of the time derivatives to a common coordinate system, the perturbation rates are summed up and integrated. The time dependence of the planets’ orbital elements are evaluated inside the time integral.

scholarly journals Long‐Term Collisional Evolution of Debris Disks

2008 ◽  
Vol 673 (2) ◽  
pp. 1123-1137 ◽  
Author(s):  
Torsten Lohne ◽  
Alexander V. Krivov ◽  
Jens Rodmann
Keyword(s):  
Debris Disks ◽  
Collisional Evolution

scholarly journals DISK RADII AND GRAIN SIZES INHERSCHEL-RESOLVED DEBRIS DISKS

2014 ◽  
Vol 792 (1) ◽  
pp. 65 ◽  
Author(s):  
Nicole Pawellek ◽  
Alexander V. Krivov ◽  
Jonathan P. Marshall ◽  
Benjamin Montesinos ◽  
Péter Ábrahám ◽  
...  
Keyword(s):  
Debris Disks ◽  
Grain Sizes

The gravitational perturbations of the Kerr black hole I. The perturbations in the quantities which vanish in the stationary state

1978 ◽  
Vol 358 (1695) ◽  
pp. 421-439 ◽  
Keyword(s):  
Black Hole ◽  
Stationary State ◽  
Weyl Tensor ◽  
Kerr Black Hole ◽  
Maxwell Field ◽  
Subsequent Work ◽  
Kerr Geometry ◽  
Gravitational Perturbations ◽  
Newman Black Hole ◽  
Basic Equations

As a preliminary towards a complete integration of the Newman-Penrose equations governing the gravitational perturbations of the Kerr black hole, the perturbations in the spin coefficients and in the components of the Weyl tensor, which vanish in the stationary state, are considered. The manner of treatment of the basic equations yields Teukolsky’s equations expressed directly in terms of the basic derivative operators of the theory and, further, suggests a preferred gauge in which two of the components of the Weyl tensor are governed by the same equations as a Maxwell field. Various identities and relations that are needed in subsequent work are assembled. In two appendixes, the solution of Maxwell’s equations in Kerr geometry and the perturbations of the charged Kerr-Newman black hole are considered.

scholarly journals Properties of small meteoroids studied by meteor video observations

2019 ◽  
Vol 621 ◽  
pp. A68 ◽  
Author(s):  
V. Vojáček ◽  
J. Borovička ◽  
P. Koten ◽  
P. Spurný ◽  
R. Štork
Keyword(s):  
Large Scale ◽  
Monochromatic Light ◽  
Light Curves ◽  
Sodium Depletion ◽  
Early Solar System ◽  
Grain Sizes ◽  
Video Observations ◽  
Small Grains ◽  
Heliocentric Orbits ◽  
Integrated Intensities

Aims. The complex study of millimetre-sized meteoroids can reveal more about the structure and origin of population of these meteoroids. Methods. Double-station video observations, paired with spectroscopic video observations, were used to study small meteoroids. In total 152 sporadic and shower meteors of maximum brightness between magnitude −5 and +3 were analysed. Spectral classification was based on time-integrated intensities of lines of Na, Mg, and Fe. Meteor light curves and deceleration were fitted by the grain erosion model. Heliocentric orbits of all meteors were computed. Monochromatic light curves were constructed in order to study differential ablation. The length of meteor wakes was evaluated as well. Results. The variety of properties among millimetre-sized meteoroids proved different sources and histories of this material. Meteoroids that contain small grains tend to release their sodium early. For given grain sizes, the sodium in Na-poor meteoroids is released earlier than in meteors without sodium depletion. Overall, meteoroids with sodium depletion are revealed to have different structures: they have stronger material without very small grains and they do not show very bright wakes. Two iron meteoroids on Halley-type orbits were observed, thereby supporting the idea of large-scale mixing of material in the early solar system. The distribution of grain sizes of Jupiter-family members was in good agreement with results from the COSIMA instrument on the ROSETTA probe.

scholarly journals A Model of Stochastic Collisions as the Cause of Clumps in Debris Disks

2004 ◽  
Vol 202 ◽  
pp. 399-401
Author(s):  
M. C. Wyatt ◽  
W. R. F. Dent ◽  
J. S. Greaves ◽  
W. S. Holland
Keyword(s):  
Simple Model ◽  
Debris Disks ◽  
Heuristic Model ◽  
Detailed Model ◽  
Debris Disk ◽  
Collisional Evolution

We present a heuristic model for the collisional evolution of material in a debris disk. This is used to consider the probability that the 2-3% brightness clump observed in the sub-mm Fomalhaut disk is caused by stochastic collisions between large planetesimals. While this simple model finds that the probability that the clump is caused by collisions is low (about 1 in 80,000), a more detailed model is required to ascertain its true likelihood.

A discussion on orbital analysis - Some problems of orbital prediction

1967 ◽  
Vol 262 (1124) ◽  
pp. 100-105
Keyword(s):  
Solar Radiation ◽  
Radiation Pressure ◽  
Solar Radiation Pressure ◽  
Atmospheric Model ◽  
Orbital Elements ◽  
Air Drag ◽  
Gravitational Perturbations ◽  
Pass Through ◽  
Orbital Analysis ◽  
Made In

Attention is paid to the problem of predicting accurately (a) the orbital elements of a balloon satellite over long periods of time, and (b) the time the satellite will pass through a given point in the orbit, a few days or weeks in advance of the event. It is shown that by computing the solar radiation pressure and gravitational perturbations of the orbit of the balloon satellite Echo 2, the orbital elements can be predicted reasonably accurately several months in advance. For the balloon satellite Explorer 19, allowing for air drag at perigee, computed from a simple atmospheric model in addition to the effect of solar radiation pressure, results in significant improvement in predicting the period of revolution a few months in advance. Finally, by numerically integrating the air-drag effect round the orbit, it is shown that a considerable improvement can be made in the accuracy of predicting the time at which a satellite will pass through a given point on the orbit.

Abnormal Grain Coarsening and Its Possible Relationship with Particle Limited Normal Grain Coarsening

2004 ◽  
Vol 467-470 ◽  
pp. 843-852 ◽  
Author(s):  
Roger D. Doherty ◽  
Elizabeth Hoffman ◽  
Christopher Hovanec ◽  
Arnaud Lens
Keyword(s):  
Grain Boundaries ◽  
High Purity ◽  
Volume Fraction ◽  
Boundary Migration ◽  
Second Phase ◽  
Grain Coarsening ◽  
Grain Sizes ◽  
Second Phase Particles ◽  
Prior Literature ◽  
Small Grains

The prior literature on abnormal grain coarsening (AGC) at low volume fractions (f) of stable second phase particles in high purity Al alloys is reviewed and reanalyzed in the light of developments in modeling particle inhibition of grain boundary migration. With the usual assumptions (i) of incoherent particles that retain their shape on contact with the grain boundaries and (ii) that all the grain boundaries are equally mobile, it appears impossible to account for process of AGC. Normal grain coarsening (NGC) is shown to be less inhibited by the particles than is AGC. This idea is explored using a new but simple model of particle inhibition by curvature removal. The curvature of the smallest grains is always larger than that of the larger grains. Two possible hypotheses to overcome this difficulty are proposed: First the possible change of shape of particles on slowly moving grain boundaries, of grains with near 14 neighbors should, after a small increment of NGC, promote AGC at low values of the volume fraction f. The second hypothesis involves the observed high density of immobile, low angle grain boundaries (LAGBs) found in recent experiments on high purity Al-Fe-Si alloys cast with very coarse grain sizes. These alloys undergo rapid AGC even at higher values of f (> 0.01). These LAGBs are expected to inhibit the shrinkage of many of the small grains, whose loss is the fundamental mechanism of NGC.

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