Sebastian Marino
This review chapter for young researchers presents our current understanding of debris discs. It introduces some of their basic properties and observables, and describes how we think they form and collisionally evolve. Special emphasis is dedicated to ALMA observations of the dust and gas, which constrains the distribution of planetesimals, their volatile composition, and potential volatile delivery to planetary atmospheres.
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Planetesimals form in gas-rich protoplanetary disks around young stars. However, protoplanetary disks fade in about 10 Myr. The planetesimals (and also many of the planets) left behind are too dim to study directly. Fortunately, collisions between planetesimals produce dusty debris disks. These debris disks trace the processes of terrestrial planet formation for 100 Myr and of exoplanetary system evolution out to 10 Gyr. This chapter begins with a summary of planetesimal formation as a prelude to the epoch of planetesimal destruction. Our review of debris disks covers the key issues, including…
In this paper we extend our numerical method for simulating terrestrial planet formation from Leinhardt and Richardson (2005) to include dynamical friction from the unresolved debris component. In the previous work we implemented a rubble pile planetesimal collision model into direct N-body simulations of terrestrial planet formation. The new collision model treated both accretion and erosion of planetesimals but did not include dynamical friction from debris particles smaller than the resolution limit for the simulation. By extending our numerical model to include dynamical friction from the …
Debris disks are optically thin, almost gas-free dusty disks observed around a significant fraction of main-sequence stars older than about 10 Myr. Since the circumstellar dust is short-lived, the very existence of these disks is considered as evidence that dust-producing planetesimals are still present in mature systems, in which planets have formed - or failed to form - a long time ago. It is inferred that these planetesimals orbit their host stars at asteroid to Kuiper-belt distances and continually supply fresh dust through mutual collisions. This review outlines observational techniques a…
HR 8799 is a four planet system that also hosts a debris disk. By numerically integrating both planets and a planetesimal disk, we find interactions between an exterior planetesimal disk and the planets can influence the lifetime of the system. We first consider resonant planetary configurations that remained stable for at least 7 Myrs sans debris disk. An exterior debris disk with only 1 per cent the mass of the outermost planet (approximately a Neptune mass) was sufficiently large enough to pull the system out of resonance after 2 to 6 Myrs. Secondly, we consider configurations which are uns…
We present the Superparticle Model/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in 3-D, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. We show that SMACK is stable to numerical viscosity and numerical heating over 10^7 yr, and that it can reproduce analytic models of disk evolution. We use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit. Differential precession create…
Two basic routes for planetesimal formation have been proposed over the last few decades. One is a classical "slow-growth" scenario. Another one is particle concentration models, in which small pebbles are concentrated locally and then collapse gravitationally to form planetesimals. Both types of models make certain predictions for the size spectrum and internal structure of newly-born planetesimals. We use these predictions as input to simulate collisional evolution of debris discs left after the gas dispersal. The debris disc emission as a function of a system's age computed in these simulat…
Post-Giant Impact Planetesimals Sustaining Extreme Debris Disks
本文通过数值模拟研究巨型撞击后形成的小行星体盘如何为极碎屑盘持续提供小颗粒尘埃，发现撞击半长轴显著影响盘的质量增量，而所有盘的碰撞率随时间以相似速率演化。
Recent simulations have shown that the formation of planets in circumbinary configurations (such as those recently discovered by Kepler) is dramatically hindered at the planetesimal accretion stage. The combined action of the binary and the protoplanetary disk acts to raise impact velocities between km-sized planetesimals beyond their destruction threshold, halting planet formation within at least 10 AU from the binary. It has been proposed that a primordial population of "large" planetesimals (100 km or more in size), as produced by turbulent concentration mechanisms, would be able to bypass …
Study of the migration of Earth-like planets in planetesimal disks and the formation of debris disks
本文研究了类地行星与行星esimal盘的相互作用，发现行星迁移后会扰动盘内行星esimal轨道，增加相对速度，导致其破碎，从而形成尘埃盘。
Several hundred stars older than 10 million years have been observed to have infrared excesses. These observations are explained by dust grains formed by the collisional fragmentation of hidden planetesimals. Such dusty planetesimal discs are known as debris discs. In a dynamically cold planetesimal disc, collisional coagulation of planetesimals produces planetary embryos which then stir the surrounding leftover planetesimals. Thus, the collisional fragmentation of planetesimals that results from planet formation forms a debris disc. We aim to determine the properties of the underlying planete…
Context: Since circumstellar dust in debris disks is short-lived, dust-replenishing requires the presence of a reservoir of planetesimals. These planetesimals in the parent belt of debris disks orbit their host star and continuously supply the disk with fine dust through their mutual collisions. Aims: We aim to understand effects of different collisional parameters on the observational appearance of eccentric debris disks. Methods: The collisional evolution of selected debris disk configurations was simulated with the numerical code ACE. Subsequently, selected observable quantities are simulat…
The similar orbital distances and detection rates of debris disks and the prominent rings observed in protoplanetary disks suggest a potential connection between these structures. We explore this connection with new calculations that follow the evolution of rings of pebbles and planetesimals as they grow into planets and generate dusty debris. Depending on the initial solid mass and planetesimal formation efficiency, the calculations predict diverse outcomes for the resulting planet masses and accompanying debris signature. When compared with debris disk incidence rates as a function of lumino…
The protoplanetary disks of Herbig Ae stars eventually dissipate leaving a tenuous debris disk comprised of planetesimals and dust, as well as possibly gas and planets. This paper uses the properties of 10-20Myr A star debris disks to consider the protoplanetary to debris disk transition. The physical distinction between these two classes is argued to rest on the presence of primordial gas in sufficient quantities to dominate the motion of small dust grains (not the secondary nature of the dust or its level of stirring). This motivates an observational classification based on the dust spectrum…
Core Accretion, the most widely accepted scenario for planet formation, postulates existence of km-sized solid bodies, called planetesimals, arranged in a razor-thin disc in the earliest phases of planet formation. In the Tidal Downsizing hypothesis, an alternative scenario for formation of planets, grain growth, sedimentation and formation of planetary cores occur inside dense and massive gas clumps formed in the outer cold disc by gravitational instability. As a clump migrates inward, tidal forces of the star remove all or most of the gas from the clump, downsizing it to a planetary mass bod…
When a protoplanetary disc loses gas, it leaves behind planets and one or more planetesimal belts. The belts get dynamically excited, either by planets ('planet stirring') or by embedded big planetesimals ('self-stirring'). Collisions between planetesimals become destructive and start to produce dust, creating an observable debris disc. Following Kenyon & Bromley (2008), it is often assumed that self-stirring starts to operate as soon as the first ~1000 km-sized embedded 'Plutos' have formed. However, state-of-the-art pebble concentration models robustly predict planetesimals between a few km …
(Abridged) A numerical model of a circumstellar debris disk is developed and applied to observations of the circumstellar dust orbiting beta Pictoris. The model accounts for the rates at which dust is produced by collisions among unseen planetesimals, and the rate at which dust grains are destroyed due to collisions. The model also accounts for the effects of radiation pressure, which is the dominant perturbation on the disk's smaller but abundant dust grains. Solving the resulting system of rate equations then provides the dust abundances versus grain size and over time. Those solutions also …
Meteorites contain minerals from Solar System asteroids with different properties (like size, presence of water, core formation). We provide new mid-IR transmission spectra of powdered meteorites to obtain templates of how mid-IR spectra of asteroidal debris would look like. This is essential for interpreting mid-IR spectra of past and future space observatories, like the James Webb Space Telescope. We show that the transmission spectra of wet and dry chondrites, carbonaceous and ordinary chondrites and achondrite and chondrite meteorites are distinctly different in a way one can distinguish i…
This paper uses observations of dusty debris discs, including a growing number of gas detections in these systems, to test our understanding of the origin and evolution of this gaseous component. It is assumed that all debris discs with icy planetesimals create second generation CO, C and O gas at some level, and the aim of this paper is to predict that level and assess its observability. We present a new semi-analytical equivalent of the numerical model of Kral et al. (2016) allowing application to large numbers of systems.That model assumes CO is produced from volatile-rich solid bodies at a…
Circumstellar disks have long been regarded as windows into planetary systems. The advent of high sensitivity, high resolution imaging in the submillimetre where both the solid and gas components of disks can be detected opens up new possibilities for understanding the dynamical histories of these systems and therefore, a better ability to place our own solar system, which hosts a highly evolved debris disk, in context. Comparisons of dust masses from protoplanetary and debris disks have revealed a stark downturn in mass in millimetre-sized grains around a stellar age of 10 Myr, ostensibly in …
Planetesimal belts are invoked to explain the prolonged existence of debris disks. Important parameters to model their collisional evolution and to compute the dust production rate are the intrinsic probability of collision $P_i$ and the mean impact velocity $U_c$. If a planet orbits close to the belt, the values of both these parameters are affected by its secular perturbations yielding a strong correlation between eccentricity $e$ and pericentre longitude $\varpi$. We adopt a new algorithm to compute both $P_i$ and $U_c$ in presence of various levels of secular correlation due to different r…
Observations of dusty debris disks can be used to test theories of planetesimal coagulation. Planetesimals of sizes up to a couple thousand kms are embedded in these disks and their mutual collisions generate the small dust grains that are observed. The dust luminosities, when combined with information on the dust spatial extent and the system age, can be used to infer initial masses in the planetesimal belts. Carrying out such a procedure for a sample of debris disks around Sun-like stars, we reach the following two conclusions. First, if we assume that colliding planetesimals satisfy a primo…
Debris discs are dusty belts of planetesimals around main-sequence stars, similar to the asteroid and Kuiper belts in our solar system. The planetesimals cannot be observed directly, yet they produce detectable dust in mutual collisions. Observing the dust, we can try to infer properties of invisible planetesimals. Here we address the question of what is the best way to measure the location of outer planetesimal belts that encompass extrasolar planetary systems. A standard method is using resolved images at mm-wavelengths, which reveal dust grains with sizes comparable to the observational wav…
Millimetre continuum observations of debris discs can provide insights into the physical and dynamical properties of the unseen planetesimals that these discs host. The material properties and collisional models of planetesimals leave their signature on the grain size distribution, which can be traced through the millimetre spectral index. We present 8.8 mm observations of the debris discs HD 48370, CPD 72 2713, HD 131488, and HD 32297 using the Australian Telescope Compact Array (ATCA) as part of the PLanetesimals Around TYpicalPre-main seqUence Stars (PLATYPUS) survey. We detect all four tar…
Debris belts on the periphery of planetary systems, encompassing the region occupied by planetary orbits, are massive analogues of the Solar system's Kuiper belt. They are detected by thermal emission of dust released in collisions amongst directly unobservable larger bodies that carry most of the debris disc mass. We estimate the total mass of the discs by extrapolating up the mass of emitting dust with the help of collisional cascade models. The resulting mass of bright debris discs appears to be unrealistically large, exceeding the mass of solids available in the systems at the preceding pr…
Debris disks are the dust disks found around ~20% of nearby main sequence stars in far-IR surveys. They can be considered as descendants of protoplanetary disks or components of planetary systems, providing valuable information on circumstellar disk evolution and the outcome of planet formation. The debris disk population can be explained by the steady collisional erosion of planetesimal belts; population models constrain where (10-100au) and in what quantity (>1Mearth) planetesimals (>10km in size) typically form in protoplanetary disks. Gas is now seen long into the debris disk phase. Some o…
Extended gaps in the debris disks of both Vega and Fomalhaut have been observed. These structures have been attributed to tidal perturbations by multiple super-Jupiter gas giant planets. Within the current observational limits, however, no such massive planets have been detected. Here we propose a less stringent `lone-planet' scenario to account for the observed structure with a single eccentric gas giant and suggest that clearing of these wide gaps is induced by its sweeping secular resonance. During the depletion of the disk gas, the planet's secular resonance propagates inward and clears a …
Observations of small extrasolar planets with a wide range of densities imply a variety of planetary compositions and structures. Currently, the only technique to measure the bulk composition of extrasolar planetary systems is the analysis of planetary debris accreting onto white dwarfs, analogous to abundance studies of meteorites. We present measurements of the carbon and oxygen abundances in the debris of planetesimals at ten white dwarfs observed with the Hubble Space Telescope, along with C/O ratios of debris in six systems with previously reported abundances. We find no evidence for carb…
Substructure evolution from protoplanetary to debris disks driven by mutually gravitating planetesimals and implications on Kepler resonances and free-floating planets
该研究提出相互引力星子的径向扩散演化图景，重现原行星盘环分布，揭示碎屑盘演化对开普勒共振链破坏及类地行星大小自由漂浮天体形成的启示。
Planet--planet scattering is a major dynamical mechanism able to significantly alter the architecture of a planetary system. In addition to that, it may also affect the formation and retention of a debris disk by the system. A violent chaotic evolution of the planets can easily clear leftover planetesimal belts preventing the ignition of a substantial collisional cascade that can give origin to a debris disk. On the other end, a mild evolution with limited steps in eccentricity and semimajor axis can trigger the formation of a debris disk by stirring an initially quiet planetesimal belt. The v…
We present new spatially resolved observations of the dust thermal emission at 7 mm from the Fomalhaut debris disk obtained with the Australia Telescope Compact Array. These observations provide the longest wavelength detection of the Fomalhaut debris disk to date. We combined the new data to literature sub-mm data to investigate the spectral index of the dust thermal emission in the sub-millimeter and constrained the $q$-slope of the power-law grain size distribution. We derived a value for $q = 3.48 \pm 0.14$ for grains with sizes around 1 mm. This is consistent with the classical prediction…
We present a new model of the $β$ Pictoris disk-and-planet system that simulates both the planetesimal collisions and the dynamics of the resulting dust grains, allowing us to model features and asymmetries in both thermal and scattered light images of the disk. Our two-part model first simulates the collisional and dynamical evolution of the planetesimals with the Superparticle-Method Algorithm for Collisions in Kuiper belts (SMACK) and then simulates the dynamical evolution of the resulting dust grains with a standard Bulirsch-Stoer N-body integrator. Given the observed inclination and eccen…
Detectable debris discs are thought to require dynamical excitation (`stirring'), so that planetesimal collisions release large quantities of dust. We investigate the effects of the secular perturbations of a planet, which may lie at a significant distance from the planetesimal disc, to see if these perturbations can stir the disc, and if so over what time-scale. The secular perturbations cause orbits at different semi-major axes to precess at different rates, and after some time t_cross initially non-intersecting orbits begin to cross. We show that t_cross is proportional to a_disc^(9/2)/(m_p…
Tidal Disruption of Planetesimals from an Eccentric Debris Disk Following a White Dwarf Natal Kick
本研究通过N体模拟表明，白矮星诞生踢可塑造偏心、近心点对齐的碎屑盘，并持续驱动星子进入潮汐瓦解轨道，从而解释白矮星金属污染。
The dust production in debris discs by grinding collisions of planetesimals requires their orbits to be stirred. However, stirring levels remain largely unconstrained, and consequently the stirring mechanisms as well. This work shows how the sharpness of the outer edge of discs can be used to constrain the stirring levels. Namely, the sharper the edge is the lower the eccentricity dispersion must be. For a Rayleigh distribution of eccentricities ($e$), I find that the disc surface density near the outer edge can be parametrised as $\tanh[(r_{\max}-r)/l_{\rm out}]$, where $r_{\max}$ approximate…
Many white dwarf stars show signs of having accreted smaller bodies, implying that they may host planetary systems. A small number of these systems contain gaseous debris discs, visible through emission lines. We report a stable 123.4min periodic variation in the strength and shape of the CaII emission line profiles originating from the debris disc around the white dwarf SDSSJ122859.93+104032.9. We interpret this short-period signal as the signature of a solid body held together by its internal strength.
Many members of nearby young moving groups exhibit infrared excess attributed to circumstellar debris dust, formed via erosion of planetesimals. With their proximity and well-dated ages, these groups are excellent laboratories for studying the early evolution of debris dust and of planetesimal belts. ALMA can spatially resolve the disk emission, revealing the location and extent of these belts, putting constraints on planetesimal evolution models, and allowing us to study planet-disk interactions. While the main trends of dust evolution in debris disks are well-known, there is almost no inform…
Planetesimals drifting through dusty and gaseous white dwarf debris discs: Types I, II and III-like migration
本文研究了星子在白矮星碎屑盘中的迁移特性，发现I型和II型迁移过慢，而微粒盘的类III型迁移在小行星或卫星产生的高质量白矮星尘埃盘中可能迅速发生，使星子能在寿命期内迁移穿越整个盘。
Testing the Impact of Planet-stirring, Self-stirring, and Mixed-stirring on Debris Disc Architecture: A Case Study of HD 16743
通过N体模拟研究HD 16743尘埃盘架构，发现巨行星esimal的混合扰动能最佳复现观测特征，且总质量约束为≥27 M_⊕。
Secondary gas in debris discs released following the decay of long-lived radioactive nuclides, catastrophic or resurfacing collisions
本文通过建模研究碎片盘中彗星体释放CO气体的机制，揭示非灾难性碰撞和放射性核素衰变可主导气体释放且与尘埃释放不成正比，并强调大型星子在年轻行星系统气体来源中的关键作用。
Debris discs consist of belts of bodies ranging in size from dust grains to planetesimals; these belts are visible markers of planetary systems around other stars that can reveal the influence of extrasolar planets through their shape and structure. Two key stirring mechanisms -- self-stirring by planetesimals and secular perturbation by an external giant planet -- have been identified to explain the dynamics of planetesimal belts; their relative importance has been studied independently, but are yet to be considered in combination. In this work we perform a suite of 286 N-body simulations exp…
Extensive photometric stellar surveys show that many main sequence stars show emission at infrared and longer wavelengths that is in excess of the stellar photosphere; this emission is thought to arise from circumstellar dust. The presence of dust disks is confirmed by spatially resolved imaging at infrared to millimeter wavelengths (tracing the dust thermal emission), and at optical to near infrared wavelengths (tracing the dust scattered light). Because the expected lifetime of these dust particles is much shorter than the age of the stars (>10 Myr), it is inferred that this solid material n…
Massive Debris Disks May Hinder Secular Stirring by Planetary Companions: An Analytic Proof of Concept
该研究通过解析模型证明，大质量碎屑盘的自引力会加速拱线进动，抑制星子偏心率，从而可能阻碍偏心行星的长期搅动，对行星推断和盘质量约束有重要意义。
We present models for the formation of terrestrial planets, and the collisional evolution of debris disks, in planetary systems that contain multiple unstable gas giants. We previously showed that the dynamics of the giant planets introduces a correlation between the presence of terrestrial planets and debris disks. Here we present new simulations that show that this connection is qualitatively robust to changes in: the mass distribution of the giant planets, the width and mass distribution of the outer planetesimal disk, and the presence of gas in the disk. We discuss how variations in these …
A debris disk is a constituent of any planetary system surrounding a main sequence star. We study whether close stellar encounters can disrupt and strip a debris disk of its planetesimals in the expanding open cluster of its birth with a decreasing star number density over 100 Myrs. Such stripping would affect the dust production and hence detectability of the disk. We tabulated the fractions of planetesimals stripped off during stellar flybys of miss distances between 100 and 1000 AU and for several mass ratios of the central to passing stars. We then estimated the numbers of close stellar en…
Motivated by debris disk studies, we investigate the gravitational microlensing of background starlight by a planetesimal disk around a foreground star. We use dynamical survival models to construct a plausible example of a planetesimal disk and study its microlensing properties using established ideas of microlensing by small bodies. When a solar-type source star passes behind a planetesimal disk, the microlensing light curve may exhibit short-term, low-amplitude residuals caused by planetesimals several orders of magnitude below Earth mass. The minimum planetesimal mass probed depends on the…
Recent observations of debris discs, believed to be made up of remnant planetesimals, brought a number of surprises. Debris disc presence does not correlate with the host star's metallicity, and may anti-correlate with the presence of gas giant planets. These observations contradict both assumptions and predictions of the highly successful Core Accretion model of planet formation. Here we explore predictions of the alternative Tidal Downsizing (TD) scenario of planet formation. In TD, small planets and planetesimal debris is made only when gas fragments, predecessors of giant planets, are tida…
This paper describes Herschel observations of the nearby (8.5pc) G5V multi-exoplanet host star 61 Vir at 70-500micron carried out by the DEBRIS survey. These reveal emission that is extended out to >15arcsec with a morphology that can be fitted by a nearly edge-on (77deg inclination) radially broad (from 30AU to >100AU) debris disk of fractional luminosity 2.7x10^-5, with two unrelated sources nearby that are more prominent at longer wavelengths. Chance alignment with a background object seen at 1.4GHz provides potential for confusion, but the star's 1.4"/yr proper motion allows Spitzer 70micr…
Since giant planets scatter planetesimals within a few tidal radii of their orbits, the locations of existing planetesimal belts indicate regions where giant planet formation failed in bygone protostellar disks. Infrared observations of circumstellar dust produced by colliding planetesimals are therefore powerful probes of the formation histories of known planets. Here we present new Spitzer IRS spectrophotometry of 111 Solar-type stars, including 105 planet hosts. Our observations reveal 11 debris disks, including two previously undetected debris disks orbiting HD 108874 and HD 130322. Combin…
Inner edges of planetesimal belts: collisionally eroded or truncated?
本文提出三阶段解析模型研究碎片盘碰撞演化，结合ALMA观测发现7个宽碎片盘中4个内边缘由碰撞侵蚀形成，3个可能被行星截断，并揭示HD 107146的宽间隙实为两个窄间隙。
In this paper we present a model of the Beta Leo debris disc, with an emphasis on modelling the resolved PACS images obtained as part of the Herschel key programme DEBRIS. We also present new SPIRE images of the disc at 250 microns, as well as new constraints on the disc from SCUBA-2, mid-IR and scattered light imaging. Combining all available observational constraints, we find three possible models for the Beta Leo (HD102647) debris disc: (i) A 2 component model, comprised of a hot component at 2 AU and a cold component from 15-70 AU. (ii) A 3 component model with hot dust at 2 AU, warm dust …
Stirred but not shaken: a multi-wavelength view of HD 16743's debris disc
本文利用HST和ALMA对HD 16743侧向碎屑盘进行多波段观测，发现其垂直尺度高度显著大于未受搅动值，表明盘内星子可能受到质量介于数倍冥王星至18.3地球质量之间的天体搅动。
Observations of debris disks offer a window into the physical and dynamical properties of planetesimals in extrasolar systems through the size distribution of dust grains. In particular, the millimeter spectral index of thermal dust emission encodes information on the grain size distribution. We have made new VLA observations of a sample of seven nearby debris disks at 9 mm, with 3" resolution and $\sim5$ $μ$Jy/beam rms. We combine these with archival ATCA observations of eight additional debris disks observed at 7 mm, together with up-to-date observations of all disks at (sub)millimeter wavel…
In recent years, a number of eccentric debris belts have been observed in extrasolar systems. The most common explanation for their shape is the presence of a nearby eccentric planetary companion. The gravitational perturbation from such a companion would induce periodic eccentricity variations on the planetesimals in the belt, with a range of precession frequencies. The overall expected shape is an eccentric belt with a finite minimum width. However, several observed eccentric debris discs have been found to exhibit a narrower width than the theoretical expectation. In this paper, we study tw…
Flares in X-ray and near infrared are observed above the quiescent emission of the supermassive black hole (SBH) in the Galactic Centre (GC) at a rate of approximately once per day. One proposed energy source for these flares is the tidal disruption of planetesimals with radius $\gtrsim 10$ km passing within $\sim$ 1 AU of the SBH. Very little is known about the formation and evolution of planetesimals in galactic nuclei such as the GC, making predictions for flaring event rates uncertain. We explore two scenarios for the formation of planetesimals in the GC: (1) in a large-scale cloud bound t…
This paper shows that the eccentric debris rings seen around the stars Fomalhaut and HD 202628 are narrower than expected in the standard eccentric planet perturbation scenario (sometimes referred to as "pericenter glow"). The standard scenario posits an initially circular and narrow belt of planetesimals at semi-major axis $a$, whose eccentricity is increased to $e_f$ after the gas disc has dispersed by secular perturbations from an eccentric planet, resulting in a belt of width $2ae_f$. In a minor modification of this scenario, narrower belts can arise if the planetesimals are initially ecce…
Planetary systems commonly survive the evolution of single stars, as evidenced by terrestrial-like planetesimal debris observed orbiting and polluting the surfaces of white dwarfs. This letter reports the identification of a circumbinary dust disk surrounding a white dwarf with a substellar companion in a 2.27 hr orbit. The system bears the dual hallmarks of atmospheric metal pollution and infrared excess, however the standard (flat and opaque) disk configuration is dynamically precluded by the binary. Instead, the detected reservoir of debris must lie well beyond the Roche limit in an optical…
We present a detailed study of the metal-polluted DB white dwarf SDSS J0845+2257 (Ton 345). Using high-resolution HST/COS and VLT spectroscopy, we have detected hydrogen and eleven metals in the atmosphere of the white dwarf. The origin of these metals is almost certainly the circumstellar disc of dusty and gaseous debris from a tidally-disrupted planetesimal, accreting at a rate of 1.6E10 gs^-1. Studying the chemical abundances of the accreted material demonstrates that the planetesimal had a composition similar to the Earth, dominated by rocky silicates and metallic iron, with a low water co…
The long-term dynamics of planetesimals in debris discs in models with parameters of binary star systems Kepler-16, Kepler-34 and Kepler-35 with planets is investigated. Our calculations have shown the formation of a stable coorbital with the planet ring is possible for Kepler-16 and Kepler-35 systems. In Kepler-34 system, significant eccentricities of the orbits of the binary and planets can to prevent the formation of such a structure. Detection circumbinary annular structures in observations of systems binary stars can be evidence of the existence of planets, retaining coorbital rings from …
A significant fraction of the mature FGK stars have cool dusty disks at least an orders of magnitudes brighter than the solar system's outer zodiacal light. Since such dusts must be continually replenished, they are generally assumed to be the collisional fragments of residual planetesimals analogous to the Kuiper Belt objects. At least 10% of solar type stars also bear gas giant planets. The fraction of stars with known gas giants or detectable debris disks (or both) appears to increase with the stellar mass. Here, we examine the dynamical evolution of systems of long-period gas giant planets…
We present an analysis of the debris disc around the nearby K2 V star HIP 17439. In the context of the Herschel DUNES key programme the disc was observed and spatially resolved in the far-IR with the Herschel PACS and SPIRE instruments. In a first model, Ertel et al. (2014) assumed the size and radial distribution of the circumstellar dust to be independent power laws. There, by exploring a very broad range of possible model parameters several scenarios capable of explaining the observations were suggested. In this paper, we perform a follow-up in-depth collisional modelling of these scenarios…
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