共查询到20条相似文献，搜索用时 46 毫秒
1.
I01 NIR Imaging Spectroscopy of Extrasolar Planets I02 Eccentricity growth in protoplanetary disks with embedded planets I03 Brown dwarf atmospheres: the dust in the L – T transition region I04 Model Atmospheres of Substellar Atmospheres at a Young Age:Influence of Gravity and Dust I05 Detection of Planetary Transits using Wavelet Analysis and Genetic Algorithms I06 Automated Difference Imaging for Extrasolar Planet Searches I07 The formation of planets around stars with various masses I08 The Multiplicity of exoplanet host stars I09 Direct imaging of planets around young stars, the case of GQ Lup b I10 On the Nucleation of NH3 under the Atmospheric Conditions of Jovian‐like Planets I11 Unveiling a new low‐mass star formation site in NGC 1333 with SCUBA I12 Linear analysis of the stability of protoplanets: Possible planetary evolutions and comparisons to the Jeans‐analysis I13 Triggered planet formation in young stellar clusters I14 Convective Radiation Fluid‐Dynamics: Formation and Early Evolution at the Substellar Limit and Beyond 相似文献
2.
Rainer Spurzem Holger Baumgardt Peter Berczik Christian Boily Stefan Deiters Pavel Kroupa Panos Patsis 《Astronomische Nachrichten》2005,326(7):589-605
G01 New evidence for a connection between massive black holes and ULX G02 Long‐Term Evolution of Massive Black Hole Binaries G03 NBODY Meets Stellar Population Synthesis G04 N‐body modelling of real globular star clusters G05 Fokker‐Planck rotating models of globular clusters with black hole G06 Observational Manifestation of chaos in spiral galaxies: quantitative analysis and qualitative explanation G07 GRAPE Clusters: Beyond the Million‐Body Problem G08 Orbital decay of star clusters and Massive Black Holes in cuspy galactic nuclei G09 An Edge‐on Disk Galaxy Catalog G10 Complexes of open clusters in the Solar neighborhood G11 Search for and investigation of new stellar clusters using the data from huge stellar catalogues G12 Computing 2D images of 3D galactic disk models G13 Outer Pseudoring in the Galaxy G14 Where are tidal‐dwarf galaxies? G15 Ultra compact dwarf galaxies in nearby clusters G16 Impact of an Accretion Disk on the Structure of a stellar cluster in active galactic nuclei G17 Order and Chaos in the edge‐on profiles of disk galaxies G18 On the stability of OB‐star configurations in the Orion Nebula cluster G19 Older stars captured in young star clusters by cloud collapse G20 General features of the population of open clusters within 1 kpc from the Sun G21 Unstable modes in thin stellar disks G22 From Newton to Einstein – Dynamics of N‐body systems G23 On the relation between the maximum stellar mass and the star cluster mass 相似文献
3.
We study spectral energy distributions of two young systems Sz54 and Sz59, that belong to Chameleon II star forming region. The results of the modeling indicate that protoplanetary disks of these systems contain gaps in the dust component. These gaps could be a result of a planetary or brown dwarf companion formation, because the companion would accumulate a disk material, moving along its orbit. In a present work we have determined physical characteristics of the disks. We also discuss possible companion characteristics, based on the geometrical parameters of the gaps. 相似文献
4.
Most main sequence stars are binaries or higher multiplicity Systems and it appears that at birth most stars have circumstellar
disks. It is commonly accepted that planetary systems arise from the material of these disks; consequently, binary and multiple
systems may have a main role in planet formation. In this paper, we study the stage of planetary formation during which the
particulate material is still dispersed as centimetre-to-metre sized primordial aggregates. We investigate the response of
the particles, in a protoplanetary disk with radius RD = 100 AU around a solar-like star, to the gravitational field of bound perturbing companions in a moderately wide (300–1600
AU) orbit. For this purpose, we have carried out a series of simulations of coplanar hierarchical configurations using a direct
integration code that models gravitational and viscous forces. The massive protoplanetary disk is around one of the components
of the binary. The evolution in time of the dust sub-disk depends mainly on the nature (prograde or retrograde) of the relative
revolution of the stellar companion, and on the temperature and mass of the circumstellar disk. Our results show that for
binary companions near the limit of tidal truncation of the disk, the perturbation leads to an enhanced accretion rate onto
the primary, decreasing the lifetime of the particles in the protoplanetary disk with respect to the case of a single star.
As a consequence of an enhanced accretion rate the mass of the disk decreases faster, which leads to a longer resultant lifetime
for particles in the disk. On the other hand, binary companions may induce tidal arms in the dust phase of protoplanetary
disks. Spiral perturbations with m = 1 may increase in a factor 10 or more the dust surface density in the neighbourhood of
the arm, facilitating the growth of the particles. Moreover, in a massive disk (0.01M⊙) the survival time of particles is
significantly shorter than in a less massive nebula (0.001M⊙) and the temperature of the disk severely influences the spiral-in
time of particles. The rapid evolution of the dust component found in post T Tauri stars can be explained as a result of their
binary nature. Binarity may also influence the evolution of circumpulsar disks.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
This review presents recent results on protoplanetary disks obtained from angularly resolved observations. Observations with mm arrays show that disks are in Keplerian rotation, with radius as large as 1000 AU. Optical images show disks to be flared. Both type of observations imply the dust in disk has evolved and grown from interstellar dust. Measurement of the gas temperature from CO isotopes indicate temperature gradient, consistent with the disk flaring and heating by the central star. Disks which appear to have started to dissipate their initial gas content have also been discovered, but their very diverse aspects leaves the dissipation process unclear. Current data mostly concern the outer disk (>50 AU), although near-IR interferometry has started to unveil the innermost regions (<1 AU). The next generation of instruments (MIDI on VLTI, ALMA) will allow to probe the intermediate regime, where planet formation is expected to occur. 相似文献
6.
F.J. Ciesla 《Icarus》2009,200(2):655-671
Large-scale radial transport of solids appears to be a fundamental consequence of protoplanetary disk evolution based on the presence of high temperature minerals in comets and the outer regions of protoplanetary disks around other stars. Further, inward transport of solids from the outer regions of the solar nebula has been postulated to be the manner in which short-lived radionuclides were introduced to the terrestrial planet region and the cause of the variations in oxygen isotope ratios in the primitive materials. Here, both outward and inward transport of solids are investigated in the context of a two-dimensional, viscously evolving protoplanetary disk. The dynamics of solids are investigated to determine how they depend on particle size and the particular stage of protoplanetary disk evolution, corresponding to different rates of mass transport. It is found that the outward flows that arise around the disk midplane of a protoplanetary disk aid in the outward transport of solids up to the size of CAIs s and can increase the crystallinity fraction of silicate dust at 10 AU around a solar mass star to as much as ∼40% in the case of rapidly evolving disks, decreasing as the accretion rate onto the star slows. High velocity, inward flows along the disk surface aid in the rapid transport of solids from the outer disk to the inner disk, particularly for small dust. Despite the diffusion that occurs throughout the disk, the large-scale, meridonal flows associated with mass transport prevent complete homogenization of the disk, allowing compositional gradients to develop that vary in intensity for a timescale of one million of years. The variations in the rates and the preferred direction of radial transport with height above the disk midplane thus have important implications for the dynamics and chemical evolution of primitive materials. 相似文献
7.
8.
Christian Theis Werner Zeilinger Susanne Hüttemeister 《Astronomische Nachrichten》2005,326(7):485-521
Posters: Because of the large number of contributions, some oral presentations had to be transferred into Posters. The reader is referred to the final programme for the actual allocation of Posters. A01 Chemical Enrichment of the Intracluster Medium A02 Structural analysis of high‐velocity clouds – Evidence for an interaction between the Milky Way and the Magellanic System A03 Multi‐Phase Chemo‐Dynamical SPH code for galaxy evolution A04 The proper motion of M33 A05 Wavelet analysis of Intra–group Light in Hickson Compact Groups A06 Evidence for an evolutionary connection between early and late type dwarf galaxies A07 Dwarf Galaxies in the NGC 5846 Group A08 X‐ray spectroscopy of serendipitous clusters of galaxies in XMM‐Newton observations A09 Evolution of smale scale systems of galaxies: X‐ray detected E+S galaxy pairs A10 Modelling Star Formation in Interacting Galaxies A11 NGC 1427A – the beginning of the end: a lonely dwarf irregular entering the dense core of the Fornax cluster A12 Dwarf galaxies in galaxy groups: Photo‐evaporation, orbits and gas stripping A13 High resolution stellar kinematics for the central component of the Polar Ring Galaxy NGC 4650A A14 The Influence of Environment on the Morphological Evolution of Disk‐Dominated Galaxies A15 Interactions and star formation in galaxies A16 Dust Condensations and Molecular Clouds in Interacting Spirals A17 Star formation rates and kinematics of modelled interacting galaxies A18 Evolution of Galaxies and the Tully–Fisher Relation A19 Evolution and Collision of Galaxies on the GRID A20 Multiwavelength observations of two S+E merger candidates: the Medusa and NGC 4441 A21 Interacting Galaxies in Small Galaxy Groups A22 Virial and total masses of galaxy triplets in the Local Supercluster A23 Simulations of Interaction Processes of Galaxies with the Intra‐Cluster Medium A24 Chemical evolution of the thick and thin disks of our Galaxy A25 Dust properties of UV‐bright galaxies at z ∼ 2 A26 Simulation of the Gravitational Collapse and Fragmentation of Rotating Molecular Clouds A27 NGC 5719/13: interacting spirals forming a counter‐rotating stellar disc A28 Starbursts in very metal‐poor dwarfs due to interactions and mergers: link to the processes in the high‐redshift young galaxies A29 Testing galaxy evolution in the field: morphology and properties of the diffuse X‐ray emission in shell galaxies A30 Effects of galactic winds on dIrrs with particular emphasis on NGC 1569 and the refill of superbubble cavities A31 Galaxy formation through merging at z ≈ 2 A32 3D simulations of the ISM‐ICM interaction of disk galaxies in clusters A33 Gas replenishment in ram pressure stripped disk galaxies A34 New Results on the Kinematics of the Outer Cluster System of NGC 1399 A35 Chemical gradient evolution in massive galaxy disk due to its minor merger with dwarf galaxy A36 The complex kinematics of galaxies in Hickson 62 A37 Dust in the outer regions of interacting galaxies A38 Dynamical interaction of M31 and M32 A39 A comparative study of galaxy properties in low‐ and high density environment A40 Compact Groups in Dense Environment: The Case of IC1370 A41 The Star Formation History of CG J1720‐67.8 A42 Galaxy populations in the infall regions of intermediate redshift clusters A43 The study of gravitational fragmentation in two‐clumps collisions A44 Star Formation Activity in Galaxy Clusters Near and Far A45 An Exploration of the Merging History of the Local Starburst Galaxy, NGC 3310 A46 The high‐velocity clouds of M31: tracers of galactic evolution A47 The Properties of Fossil Groups 相似文献
9.
T. V. Demidova 《Solar System Research》2018,52(2):180-188
The formation of a planetary system from the protoplanetary disk leads to destruction of the latter; however, a debris disk can remain in the form of asteroids and cometary material. The motion of planets can cause the formation of coorbital structures from the debris disk matter. Previous calculations have shown that such a ring-like structure is more stable if there is a binary star in the center of the system, as opposed to a single star. To analyze the properties of the coorbital structure, we have calculated a grid of models of binary star systems with a circumbinary planet moving in a planetesimal disk. The calculations are performed considering circular orbits of the stars and the planet; the mass and position of the planet, as well as the mass ratio of the stars, are varied. The analysis of the models shows that the width of the coorbital ring and its stability significantly depend on the initial parameters of the problem. Additionally, the empirical dependences of the width of the coorbital structure on the parameters of the system have been obtained, and the parameters of the models with the most stable coorbital structures have been determined. The results of the present study can be used for the search of planets around binary stars with debris disks. 相似文献
10.
Conventional planet formation models via coagulation of planetesimals require timescales in the range of several 10 or even 100 Myr in the outer regions of a protoplanetary disk. But according to observational data, the lifetime of a protoplanetary disk is limited to about 6 Myr. Therefore the existence of Uranus and Neptune poses a problem. Planet formation via gravitational instability may be a solution for this discrepancy. We present a parameter study of the possibility of gravitationally triggered disk instability. Using a restricted N‐body model which allows for a survey of an extended parameter space, we show that a passing dwarf star with a mass between 0.1 and 1 M⊙ can probably induce gravitational instabilities in the pre‐planetary solar disk for prograde passages with minimum separations below 80‐170 AU. Inclined and retrograde encounters lead to similar results but require slightly closer passages. Such encounter distances are quite likely in young moderately massive star clusters. The induced gravitational instabilities may lead to enhanced planetesimal formation in the outer regions of the protoplanetary disk, and could therefore be relevant for the formation of Uranus and Neptune. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
《Planetary and Space Science》2007,55(5):569-581
We discuss selected possibilities to detect planets in circumstellar disks. We consider the search for characteristic signatures in these disks caused by the interaction of giant planets with the disk as the most promising approach. Numerical simulations show that these signatures are usually much larger in size than the planet itself and thus much easier to detect. The particular result of the planet–disk interaction depends on the evolutionary stage of the disk. Primary signatures of planets embedded in disks are gaps in the case of young disks and characteristic asymmetric density patterns in debris disks.We present simulations which demonstrate that high spatial resolution observations performed with instruments/telescopes that will become available in the near future will be able to trace the location and other properties of young and evolved planets. These observations will allow to directly investigate the formation and evolution of planets in protoplanetary and debris disks. 相似文献
12.
13.
We numerically model the evolution of dust in a protoplanetary disk using a two-phase (gas+dust) Smoothed Particle Hydrodynamics
(SPH) code, which is non-self-gravitating and locally isothermal. The code follows the three dimensional distribution of dust
in a protoplanetary disk as it interacts with the gas via aerodynamic drag. In this work, we present the evolution of a disk
comprising 1% dust by mass in the presence of an embedded planet for two different disk configurations: a small, minimum mass
solar nebular (MMSN) disk and a larger, more massive Classical T Tauri star (CTTS) disk. We then vary the grain size and planetary
mass to see how they effect the resulting disk structure.
We find that gap formation is much more rapid and striking in the dust layer than in the gaseous disk and that a system with
a given stellar, disk and planetary mass will have a different appearance depending on the grain size and that such differences
will be detectable in the millimetre domain with ALMA. For low mass planets in our MMSN models, a gap can open in the dust
disk while not in the gas disk. We also note that dust accumulates at the external edge of the planetary gap and speculate
that the presence of a planet in the disk may facilitate the growth of planetesimals in this high density region. 相似文献
14.
《New Astronomy》2003,8(5):401-414
Recently, Brittain and Rettig, using the cryogenic echelle spectrograph at the Infrared Telescope Facility to study the infrared emission from the inner preplanetary disk of the Herbig Ae/Be star HD141569, detected CO and H3+ ion emission. This emission has been tentatively interpreted as due to the existence of a forming gas giant planet. The suggested protoplanetary blob appears to be orbiting its host star at about 7 AU being perhaps 2 AU across and roughly five times the mass of Jupiter. Based on numerical modeling of the evolution of the dust disk we show that their observational results are compatible with the presence of an evolved giant vortex in the disk. Our calculations suggest that vortices formed in disks similar to the one found around HD141569 are more effective at capturing solid material than equivalent structures around solar-like stars. On the other hand, we investigate the possibility to find evidence for large-scale vortices in preplanetary disks by submillimeter interferometry. Disks around Herbig Ae/Be stars may be primary targets for giant vortex detection using this technique. 相似文献
15.
《Astronomische Nachrichten》2005,326(7):647-674
P01 Calibrations on DSS‐II Plates P02 High‐Resolution Near‐Infrared Speckle Interferometry and Radiative Transfer Modeling of the OH/IR star OH 26.5 + 0.6 P03 Mid‐infrared long‐baseline interferometry of the symbiotic Mira star RX Pup with the VLTI/MIDI instrument P04 N2D+ abundance in high mass star forming regions P05Causal Viscosity in Accretion Disc Boundary layers P06 Planetesimals in protoplanetary disks P07 Star Clusters in the Large Magellanic Cloud P08 Is there a universal mass function? P09 On CO cooling in dense molecular clouds P10 An unbiased search for molecular clumpuscules P11 Vertical structure of accretion disks P12 A New Data Acquisition System and User Control Program for CCD Cameras at “Hoher List” Observatory P13 Tracing the Photon Dominated Region around DR21 with CO, CI, CII, and OI emission P14 Time resolved spectroscopy of CI Aql P15 Empirical Color Transformations between SDSS Photometry and Other Photometric Systems P16 V4332 Sgr P17 Low rotation velocities of white dwarfs from the CaII K line P18 E‐Learning in Astronomy P19 RR Lyrae stars: Kinematics, orbits and z‐distribution P20 New developments on the field of chemically peculiar stars in the milky way and the LMC P21 Large‐scale CO Mapping of the CEPHEUS Giant Molecular Cloud using KOSMA P22 HoLiCS II – The “Hoher List Control System” II P23 88 GHz “Holotransmitter” for the Nanten2 Telescope P24 Comet Astrometry – Tracing the last witnesses of the solar system's childhood P25 Considerations on the spectral appearance of M‐type brown dwarfs P26 Photon Dominated Region Modelling of Barnard 68 P27 A New Versatile Multichannel CCD‐Controller for BUSCA P28 High Precision “Bonn Shutters” for the largest CCD Mosaic Cameras P29 High‐Resolution Near‐Infrared Speckle Interferometry and Radiative Transfer Modeling of the OH/IR star OH 104.9 + 2.4 P30 A new Doppler image of the weak‐line T Tauri star V410 Tauri P31 Improving our knowledge on open cluster radial velocities P32 The Distribution of MSX Infrared Dark Clouds in the inner Milky Way P33 Was the Early Earth shielded from UV by Ozone produced from the Smog Mechanism? P34 Structure Analysis of the CO data in the Perseus clouds P35 Evidence for Turbulence in the Velocity Fields of Perseus Cores P36 Dust‐driven Winds and Their Resulting Mass Loss at Subsolar Metallicity P37 Two adjacent gigantic (∼9°) IRAS filaments of bipolar morphology: An almost invisible pair P38 A new optical filament of the Monogem Ring P39 The Far Ultraviolet Spectroscopic Explorer Survey of OVI Emission in the Milky Way 相似文献
16.
Abstract– A new view of disk evolution is emerging from self‐consistent numerical simulation modeling of the formation of circumstellar disks from the direct collapse of prestellar cloud cores. This has implications for many aspects of star and planet formation, including the growth of dust and high‐temperature processing of materials. A defining result is that the early evolution of a disk is crucially affected by the continuing mass loading from the core envelope, and is driven into recurrent phases of gravitational instability. Nonlinear spiral arms formed during these episodes fragment to form gaseous clumps in the disk. These clumps generally migrate inward due to gravitational torques arising from their interaction with a trailing spiral arm. Occasionally, a clump can open up a gap in the disk and settle into a stable orbit, revealing a direct pathway to the formation of companion stars, brown dwarfs, or giant planets. At other times, when multiple clumps are present, a low mass clump may even be ejected from the system, providing a pathway to the formation of free‐floating brown dwarfs and giant planets in addition to low mass stars. Finally, it has been suggested that the inward migration of gaseous clumps can provide the proper conditions for the transport of high‐temperature processed solids from the outer disk to the inner disk, and even possibly accelerate the formation of terrestrial planets in the inner disk. All of these features arising from clump formation and migration can be tied together conceptually in a migrating embryo model for disk evolution that can complement the well‐known core accretion model for planet formation. 相似文献
17.
18.
Philip J.Armitage Ian A.Bonnell 《Monthly notices of the Royal Astronomical Society》2002,330(1):L11-L14
We show that the dearth of brown dwarfs in short-period orbits around Solar-mass stars – the brown dwarf desert – can be understood as a consequence of inward migration within an evolving protoplanetary disc. Brown dwarf secondaries forming at the same time as the primary star have masses which are comparable to the initial mass of the protoplanetary disc. Subsequent disc evolution leads to inward migration, and destruction of the brown dwarf, via merger with the star. This is in contrast with massive planets, which avoid this fate by forming at a later epoch when the disc is close to being dispersed. Within this model, a brown dwarf desert arises because the mass at the hydrogen-burning limit is coincidentally comparable to the initial disc mass for a Solar mass star. Brown dwarfs should be found in close binaries around very low mass stars, around other brown dwarfs, and around Solar-type stars during the earliest phases of star formation. 相似文献
19.
M. Jura 《Astrophysics and Space Science》1997,251(1-2):81-88
We propose that at least two stars on or near the AGB have long-lived orbiting disks: HD 44179, the central star in the Red
Rectangle, and BM Gem, a carbon-rich star with an oxygen-rich circumstellar envelope. The CO emission from both of these disks
has a spike with a width near ∼2 km s−1, indicating disk radii of ∼1016 cm. The dust in such disks is therefore quite cold (near T ∼ 50 K for the Red Rectangle) and may emit primarily at submillimeter
wavelengths. The disks around stars where there is also substantial mass loss may not be easily observable; there could be
many as yet undiscovered disks around AGB stars
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
20.
The Hill stability criterion is applied to analyse the stability of a planet in the binary star system of HD 41004 AB, with the primary and secondary separated by 22 AU, and masses of 0.7 M⊙ and 0.4 M⊙, respectively. The primary hosts one planet in an S‐type orbit, and the secondary hosts a brown dwarf (18.64 MJ) on a relatively close orbit, 0.0177 AU, thereby forming another binary pair within this binary system. This star‐brown dwarf pair (HD 41004 B+Bb) is considered a single body during our numerical calculations, while the dynamics of the planet around the primary, HD 41004 Ab, is studied in different phase‐spaces. HD 41004 Ab is a 2.6 MJ planet orbiting at the distance of 1.7 AU with orbital eccentricity 0.39. For the purpose of this study, the system is reduced to a three‐body problem and is solved numerically as the elliptic restricted three‐body problem (ERTBP). The Hill stability function is used as a chaos indicator to configure and analyse the orbital stability of the planet, HD 41004 Ab. The indicator has been effective in measuring the planet's orbital perturbation due to the secondary star during its periastron passage. The calculated Hill stability time series of the planet for the coplanar case shows the stable and quasi‐periodic orbits for at least ten million years. For the reduced ERTBP the stability of the system is also studied for different values of planet's orbital inclination with the binary plane. Also, by recording the planet's ejection time from the system or collision time with a star during the integration period, stability of the system is analysed in a bigger phase‐space of the planet's orbital inclination, ≤ 90°, and its semimajor axis, 1.65–1.75 AU. Based on our analysis it is found that the system can maintain a stable configuration for the planet's orbital inclination as high as 65° relative to the binary plane. The results from the Hill stability criterion and the planet's dynamical lifetime map are found to be consistent with each other. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献