Planets form in the circumstellar disks of young stars. We review the basic physical processes by which solid bodies accrete each other and alter each others' random velocities, and we provide order-of-magnitude derivations for the rates of these processes. We discuss and exercise the two-groups approximation, a simple yet powerful technique for solving the evolution equations ...
NASA Astrophysics Data System (ADS)
"Transitional" T Tauri disks have optically thin holes with radii gsim10 AU, yet accrete up to the median T Tauri rate. Multiple planets inside the hole can torque the gas to high radial speeds over large distances, reducing the local surface density while maintaining accretion. Thus multi-planet systems, together ...
Clean up of small bodies which were not accreted onto protoplanetswas the last and longest stage in planet formation.After oligarchy, protoplanets cleared wide gaps around theirorbits whichshut off the accretion of small bodies from just outside their Hillradii. Gravitational instability in the disk of small bodies producedlarger ones whose random ...
We address three questions regarding solar system planets: What determined their number? Why are their orbits nearly circular and coplanar? How long did they take to form? Runaway accretion in a disk of small bodies resulted in a tiny fraction of the bodies growing much larger than all the others. These big bodies dominated the viscous stirring of all bodies. Dynamical ...
I report the results of a three-year intensive radial-velocity survey of 22 planet-host stars in search of the low-amplitude (K 5-10 m/s) signals from additional planets which may be "hiding" in the residuals of the known planet orbital solution. On average, more than 40 radial-velocity observations were obtained for each target using the High-Resolution Spectrograph at the 9.2m Hobby-Eberly ...
Feb 2, 2011 ... You are here: AB Home � Articles � A Six-Planet System. About Astrobiology � Funding Opportunities � Focus Groups � Education and Outreach ...
NASA Website
Direct imaging searches have begun to achieve significant sensitivity to giant planets at large separations (> 100 AU) from their host stars. Such searches motivate the exploration of planetary formation and evolution models that predict the number, masses, and orbital properties of planets which may reside in wide orbits. The standard formation models of core accretion and ...
There exists strong circumstantial evidence from their eccentric orbits that most of the known extra-solar planetary systems are the survivors of violent dynamical instabilities. Here we explore the effect of giant planet instabilities on the formation and survival of terrestrial planets. We numerically simulate the evolution of planetary systems around Sun-like stars that include three ...
This dissertation explores three distinct projects in the field of planetary formation and evolution: type I migration, cessation of mass accretion, and the atmospheric dynamics of hot Jupiters. All three of these projects touch on outstanding or unresolved issues in the field. Each attempts to unify analytic and numerical approaches in order to physically motivate solutions ...
The existence of an accretion column in 32 Cyg is reported, and the presence of the accretion column
NASA Technical Reports Server (NTRS)
With IXO, spectroscopy of accretion onto black holes will finally rival optical and IR spectroscopy of accreting young stars. ...
accretion disks in the western Gulf region (Texas and Louisiana). Accretion ... protostellar disks are believed to be accretion disks associated with young, ...
stars via accretion. A necessary condition for accretion growth of a hy- ... via accretion for stars more massive than 1 M@. 1. Introduction ...
accretion? " What is the structure of the inner disk? " How do accretion disks drive jets? ... IXO will reveal the physics of disk accretion, and low L_X ...
Observations of T Tauri stars and young brown dwarfs suggest that the accretion rates of their disks
We calculate the structure of an effectively optically thin and geometrically thin accretion disk in
) #12;IV: Fueling AGN: Hot vs. Cold Gas Accretion #12;Hot vs. Cold Accretion Bondi accretion vs. jet power: accretion flow or jet? � The 3CRR sample of radio galaxies � An accretion-flow mode dichotomy in RL AGN � Fueling AGN: Cold vs. hot gas accretion � ...
E-print Network
A model for disk accretion by a rotating magnetic neutron star is proposed which includes a detailed
A possible accretion model associated with the ionization instability of quasar disks is proposed to
A model of the accumulation process of a satellite about an accreting planet is proposed in order to
of a Medicean "financial oligarchy" in the domain of state finance, with extremely personal and highly
High Energy Astrophysics: Accretion Disks II 1/59 Accretion Disks II 1 The dynamical equations Astrophysics: Accretion Disks II 2/59 The simplest accretion disc model to construct is that of the thin disc on the azimuthal angle z #12;High Energy Astrophysics: Accretion Disks II 3/59 � The ...
High Energy Astrophysics: Accretion Disks I 1/60 Accretion Disks I References: Accretion Power in Astrophysics, J. Frank, A. King and D. Raine. High Energy Astrophysics, Vol. 2, M.S. Longair, Cambridge Astrophysics: Accretion Disks I 2/60 1 Overview Accretion disks are important in a number of ...
data yield the accretion disk thickness, diameter, electron density, and magnetic field. Introduction. The structure of AGN accretion disks on sub-parsec ...
formation of massive stars via accretion. A necessary condition for accre- ... constraints on the accretion rate necessary to produce high mass stars and ...
The structure of AGN accretion disks on sub-parsec scales can be probed t,hrough ... GHz to map absorption caused by an inner accretion disk. ...
Nov 19, 2004 ... In an accretion disk, material near the outside moves slower than ... Depending on the angle at which we observe the accretion disk, ...
Jan 29, 2010 ... KY Relativistic Accretion Disk models. A set of models from Dovciak et al. (2004 ) for accretion disk spectra in the strong gravity regime. ...
do not have accretion disks. Optical spectra are the only way that we can .... inner accretion disks) confirms the asymmetrical distribution of such stars ...
large radius with `low' a.m. (e.g. from interstellar medium) but still has far too much a.m. to accrete. Capture rate is an upper limit to the accretion ...
I review the X-ray observations of galactic accreting black holes and neutron stars and interpretations of these in terms of solutions of the accretion flow equations. PMID:12804240
PubMed
Nov 6, 2000 ... "accretion" means collecting of additional material. Two major places where astronomers see accretion disks are in binary star systems (two ...
Sep 27, 2002 ... Accretion Disk Simulation ... Instead, the graphic shows spiral shock waves in a three dimensional simulation of an accretion disk -- material ...
XTE(ASM) and BATSE links to Accreting Pulsars. Last Updated: December 6, 2002 ... Undetermined Companion, Anomalous X-ray Pulsars (non-accretion objects) ...
Sep 4, 1998 ... 3. Formation of an Accretion Disk. Bonnet-Bidaud and van der Klis (1979) showed that even if the accretion is from the stellar wind, ...
Numerical simulations of planetary accretion have succeeded in matching most of the physical and orbital properties of the terrestrial planets with one glaring exception: they categorically form Mars analogs that are roughly an order of magnitude too massive (Raymond et al. 2009). The initial conditions that best reproduce the mass of Mars require that the inner planetesimal ...
Ice accretion calculations were made for a modern commercial transport using the NASA Lewis LEWICE3D ice accretion code. The ice accretion calculations were made for the wing and horizontal tail using both isolated flow models and flow models incorporatin...
National Technical Information Service (NTIS)
107 Chapter 5 The Effects of Ballistic Accretion on a Protobinary System In Chapter 4, a method on the parameters of a protobinary system are studied by considering simple ballistic accretion of particles sizes of the protostars. In this chapter, ballistic accretion calculations are performed to cover a much
Bain's model for the calculation of ice accretion rates was compared with meteorological flight data. The Bain model for the determination of the ice accretion rate on cylindrical rods is extended to the calculation of the accretion shape and velocity in ...
Bain's model for the calculation of ice accretion rates was compared with meteorological flight data. The Bain model for the determination of the ice accretion rate on cylindrical rods was extended to the calculation of the accretion shape and velocity in...
