Phoenix Giants are first-ascent giant stars orbited by substantial dusty and gaseous disks that are sometimes accreting onto the central star. We present the characterization of two dusty first-ascent giant stars identified through cross-correlating the Tycho-2 and IRAS catalogs. CD-30 11814 ...

2S 0918-549 is a low-mass X-ray binary (LMXB) with a low optical to X-ray flux ratio. Probably it is an ultracompact binary with an orbital period shorter than 60 min. Such binaries cannot harbor hydrogen rich donor stars. As with other (sometimes confirmed) ultracompact LMXBs, 2S 0918-549 is observed to have a high neon-to-oxygen abundance ratio (Juett et al. 2001, ApJ, 560, L59) which has been ...

We present the discovery of a super lithium-rich K giant star, G0928+73.2600. This red giant (T eff = 4885 K and log g = 2.65) is a fast rotator with a projected rotational velocity of 8.4 km s-1 and an unusually high lithium abundance of A(Li) = 3.30 dex. Although the lack of a measured parallax precludes knowing the exact evolutionary phase, an ...

The present calculation of giant planet evolution proceeds under the hypothesis that the solid cores

An abundance analysis for 35 chemical elements based on a high-resolution (R = 67000) optical spectra of two metal-poor ([Fe/H] ~ - 1.50) halo red giants, HD232078 and HD218732, is presented. Abundances of 10 chemical elements were derived for the first time. Both red giants are chromospherically active and optically variable, located close to the red ...

We have conducted a near-infrared monitoring campaign at the UK Infrared Telescope, of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In ...

In this Letter, we report on a low-resolution spectroscopic survey for Li-rich K giants among 2000 low-mass (M <= 3 M sun) giants spanning the luminosity range from below to above the luminosity of the clump. Fifteen new Li-rich giants including four super Li-rich K giants (log epsilon(Li) >=3.2) were ...

The core accretion mechanism of giant planet formation has been used to explain ... system earth and planetary science letters earth and planetary science ...

Recently, Ida et al. made an N-body simulation of lunar accretion from a protolunar disk formed by a

Dec 19, 1999 ... Here gas from a blue giant star is shown being stripped away into an accretion disk around its compact binary companion. ...

Ideas about the accretion and early evolution of the Earth and the other terrestrial planets have recently undergone a number of revolutionary changes. It has become clear that giant impacts were far from rare events. In the later stages of accretion any ...

competitors; the style of growth is not oligarchy, but monarchy. Keywords: Accretion, giant planets, planetesimals. 1. Introduction ...

It is proposed a new mechanism for high energy gamma ray burst in Supernova type I (SNI) explosion. Presupernova is assumed to be a binary system comprised of a red giant and a white dwarf with a wind accretion. The accretion flow terminates by the accret...

Models were developed to simulate planet formation. Three major phases are characterized in the simulations: (1) planetesimal accretion rate, which dominates that of gas, rapidly increases owing to runaway accretion, then decreases as the planet's feeding...

USGS/CVO Logo, click to link to National USGS Website Cascades Volcano Observatory, Vancouver, Washington Volcanoes and History Cascade Range Volcanoes First Ascents and...

it. For a given core mass the properties of such core�envelope proto giant planets are largely the masses of Uranus and Neptune but below the masses of Jupiter and Saturn. If a proto giant planet arrives' proto giant planets still fall short of Jupiter and Saturn, an indication, that gas�accretion has

This paper extends our previous study of planet/brown dwarf accretion by giant stars to solar-mass stars located on the red giant branch. The model assumes that the planet is dissipated at the bottom of the convective envelope of the giant star. The evolution of the giant is then followed in ...

Jun 30, 2005 ... World with giant core bolsters planet-formation theory ... With the "core accretion" theory, planets start as small rock-ice cores that grow ...

This project investigates the origin of giant planets, both in the Solar System and around other stars. It is assumed that the planets form by the core accretion process: small solid particles in a disk surrounding a young star gradually coagulate into ob...

We have investigated how envelope pollution by icy planetesimals affects the critical core mass for gas giant formation and the gas accretion time-scales. In the core-accretion model, runaway gas accretion is triggered after a core reaches a critical core mass. All the previous studies on the ...

We have investigated how envelope pollution by icy planetesimals affects the critical core mass for gas giant formation and the gas accretion time-scales. In the core-accretion model, runaway gas accretion is triggered after a core reaches a critical core mass. All the previous studies on the ...

Gas giant planets play a fundamental role in shaping the orbital architecture of planetary systems and in affecting the delivery of volatile materials to terrestrial planets in the habitable zones. Current theories of gas giant planet formation rely on either of two mechanisms: the core accretion model and the disk instability model. ...

Some aspects of hot spots or giant flares on supermassive accretion disks are investigated, with particular emphasis on the circumstances under which the orbital motion of such a spot can lead to a quasi-linear rate of rotation of the polarization position angle. A tentative interpretation of recent polarization observations of AO 0235+164 is given, and ...

A model is proposed for nonsteady disk accretion in the Galaxy due to dynamical friction, and it is applied to analyze how dynamical friction will affect the galactic motion of giant molecular clouds. Comparison with the observed gas distribution in the galactic disk imposes stringent constraints on the physical parameters of a typical cloud.

Recent surveys confirm early results about a deficiency or even absence of CN-strong stars on the asymptotic giant branch (AGB) of globular clusters (GCs), although with quite large cluster-to-cluster variations. In general, this is at odds with the distribution of CN band strengths among first ascent red giant ...

In just two orbits, the number, temperatures, and luminosities of red giants at 1.8 R_e in M32 will be fully revealed by combining NICMOS 1.6Mu images with this team's previous WFPC2 V and I data {Grillmair et al. 1996, AJ, 112, 1975; GTO 5435}. The resulting I-H color-magnitude data will test the reality of infrared-bright giants seen in ground-based ...

to be considered when estimating young giant planet properties at pre�main sequence stellar ages, respectively, together with the Saturn�mass proto giant planet (dashed) that has been calculated according: A Saturn mass proto gi� ant planet with the main accretion nucleated after 9 Myr almost outshines a 0:1 M

The evolution of the distribution of giant molecular clouds in galaxies under the influence of dynamical friction on stars and viscosity is calculated in the approximation of a collisionless gas. It is shown that in principle the joint action of the viscosity and the dynamical friction can lead to the formation of the ring-shaped distribution of giant ...

Magnetospheric accretion is an important process for a wide range of astrophysical systems and may play a role in the formation of gas giant planets. Extending the formalism describing stellar magnetospheric accretion into the planetary regime, we demonstrate that magnetospheric processes may govern accretion onto ...

In the standard model of gas giant planet formation, a large solid core (~10 times the Earth's mass) forms first, then accretes its massive envelope (100 or more Earth masses) of gas. However, inward planet migration due to gravitational interaction with the protostellar gas disk poses a difficulty in this model. Core-sized bodies undergo rapid ``type I'' ...

In this study we present abundances of 12C, 13C, N, O and up to 26 other chemical elements in two first-ascent giants and two core-helium-burning 'clump' stars of the open cluster NGC 2506. Abundances of carbon were derived using the C2 Swan (0,1) band head at 5635.5 �. The wavelength interval 7940-8130 �, with strong CN features, was analysed in order ...

In this study we present abundances of 12C, 13C, N, O and up to 26 other chemical elements in two first-ascent giants and two core-helium-burning 'clump' stars of the open cluster NGC 2506. Abundances of carbon were derived using the C2 Swan (0,1) band head at 5635.5 �. The wavelength interval 7940-8130 �, with strong CN features, was analysed in order ...

One possible mechanism for giant planet formation is disk instability in which the planet is formed as a result of gravitational instability in the protoplanetary disk surrounding the young star. The final composition and core mass of the planet will depend on the planet's mass, environment, and the planetesimal accretion efficiency. We calculate ...

Recently, Ida et al. made an N-body simulation of lunar accretion from a protolunar disk formed by a giant impact. One of their important conclusions is that the accretion time of the Moon is as short as one month. Such rapid accretion is a necessary consequence of the high surface density of a lunar mass disk ...

Overview of Terrestrial Planet Formation; Solar System terrestrial planets; Other Systems ... Late-stage accretion. Late veneer . Giant planets form ...

Gas giant planets have been detected in orbit around an increasing number of nearby stars. Two theories have been advanced for the formation of such planets: core accretion and disk instability. Core accretion, the generally accepted mechanism, requires several million years or more to form a gas giant planet in a ...

This site offers a powerpoint presentation describing astronomers current theory on the formation of our solar system. It contains slides describing star formation, protostars, the accretion of propoplanetary disks, the formation of gas giants and terrestrial planets, and the formation of bodies beyond the planets.

Oct 6, 2010 ... After the planets were constructed the Solar System still teemed with the detritus of planet formation--planetesimals that had not accreted ...

Given their range of volatilities, alkali elements are potential tracers of temperature-dependent processes during planetary accretion and formation of the Earth-Moon system. Under the giant impact hypothesis, no direct connection between the composition ...

. Magnetic materials. EMF. Faraday's law and the dynamo principle. Inductance and transformers. P.1.2b, accretion disks: disk temperature and spectral response, aspects of nuclear burning, supernovae

The final stage of terrestrial planet formation is known as the giant impact stage where protoplanets collide with one another to form planets. So far this stage has been mainly investigated by N-body simulations with an assumption of perfect accretion in which all collisions lead to accretion. However, this assumption breaks for ...

We study the formation of a giant gas planet by the core-accretion gas-capture process, with numerical simulations, under the assumption that the planetary core forms in the center of an anti-cyclonic vortex. The presence of the vortex concentrates particles of centimeter to meter size from the surrounding disk, and speeds up the core formation process. ...

We investigate the tidal interactions of a red giant with a main sequence in the dense stellar core of globular clusters by Smoothed Particle Hydrodynamics method. Two models of $0.8 \\msun$ red giant with the surface radii 20 and $85 R_\\sun$ are used with 0.6 or $0.8M_\\sun$ main sequence star treated as a point mass. We demonstrate that even for the ...

for growing core) are in the range of 10 to 15 earth masses, for standard (minimum mass) assumptions about core mass from about 13 to 7:2 Earth�masses. 3. Envelope accretion at various orbital radii The early that is needed to initiate gas accretion to a few hundred earth masses at various orbital radii. Figure 2

I calculate the specific angular momentum of mass accreted by a binary system embedded in the dense wind of a mass-losing asymptotic giant branch star. The accretion flow is of the Bondi-Hoyle-Lyttleton type. For most of the space of the relevant parameters the flow is basically an isothermal high Mach number ...

I calculate the specific angular momentum of mass accreted by a binary system embedded in the dense wind of a mass losing asymptotic giant branch star. The accretion flow is of the Bondi-Hoyle-Lyttleton type. For most of the relevant parameters space the flow is basically an isothermal high Mach number accretion ...

Although Roche lobe overflow scenarios are usually quoted in relation with barium stars the authors show that a wind accretion model is better suited for explaining the barium phenomenon. This model assumes that barium stars result from the accretion of part of the matter ejected through a wind and a planetary nebula by a heavy element-rich asymptotic ...

While the population of main-sequence debris discs is well constrained, little is known about debris discs around evolved stars. This paper provides a theoretical framework considering the effects of stellar evolution on debris discs, particularly the production and loss of dust within them. Here, we repeat a steady-state model fit to disc evolution statistics for main-sequence A stars, this time ...

The mass acquired by a gas giant planet has long been believed to result from accretion of material within the surrounding gaseous disk (nebula). Bate, D'Angelo, and I have analyzed the properties and consequences of this flow by means of three-dimensional hydrodynamical simulations. Most of the accretion occurs after the planet has ...

IUE observations were begun for a two-year program to monitor the UV variability of three interacting peculiar red giant (PRG) binaries, HD 59643 (C6,2), HD 35155 (S3/2), and HR 1105 (S3.5/2.5). All of these systems were suspected to involve accretion of ...

February 2009 Keywords: Giant planets Planet formation Jupiter Saturn Uranus Neptune a b s t r a c mostly on whether they switched position during the instability phase. For Uranus, the accreted mass is 0:015 M� in models in which it is initially closer to the Sun than Uranus, and 0:066 � 0:006 M� otherwise

The influence of dynamical friction on stars on the global distribution of giant molecular clouds in galaxies is calculated in different model approximations. It is shown that in their Galaxy dynamical friction alone cannot lead to the formation of the observed ring-shaped distribution of the giant molecular clouds during a time comparable with the age of ...

We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U-band observations. Our study comprises 95 members of the {approx}4 Myr old cluster Tr 37 (including 20 'transition' objects (TOs)), as well as the only classical T Tauri star (CTTS) in the {approx}12 Myr old cluster NGC 7160. The stars show different disk ...

The Mira AB system is a nearby (~107 pc) example of a wind accreting binary star system. In this class of system, the wind from a mass-losing red giant star (Mira A) is accreted onto a companion (Mira B), as indicated by an accretion shock signature in spectra at ultraviolet and X-ray wavelengths. Using novel ...

Transit observations indicate a large dispersion in the internal structure among the known gas giants. This is a big challenge to the conventional sequential planetary formation scenario because the diversity is inconsistent with the expectation of some well defined critical condition for the onset of gas accretion in this scenario. We suggest that ...

We perform hydrodynamical simulations of the accretion of pebbles and rocks on to protoplanets of a few hundred kilometres in radius, including two-way drag force coupling between particles and the protoplanetary disc gas. Particle streams interacting with the gas within the Hill sphere of the protoplanet spiral into a prograde circumplanetary disc. Material is ...

Several models exist to describe the growth and evolution of Earth; however, variables such as the type of precursor materials, extent of mixing, and material loss during accretion are poorly constrained. High-precision palladium-silver isotope data show that Earth's mantle is similar in 107Ag/109Ag to primitive, volatile-rich chondrites, suggesting that Earth ...

Several models exist to describe the growth and evolution of Earth; however, variables such as the type of precursor materials, extent of mixing, and material loss during accretion are poorly constrained. High-precision palladium-silver isotope data show that Earth�s mantle is similar in 107Ag/109Ag to primitive, volatile-rich chondrites, suggesting that Earth ...

Hot intracluster gas associated with clusters of galaxies can cool and accrete into stationary or slowly moving giant galaxies near the cluster center. Enhanced soft X-ray emission and faint extranucler optical emission lines observed in M87 (in the Virgo cluster) and NGC 1275 (in the Perseus cluster) strongly suggest that this process is occurring. In ...

The giant planets' solid cores must have formed prior to the dispersal of the primordial solar nebula, to allow the capture of their massive, gaseous envelopes from the nebula. Recent observations of disks of dust surrounding nearby solar-like stars lead to estimates of nebula lifetimes at 106 to 107 years. Thus, theories of solid particle accretion must ...

We combine variability information from the MAssive Compact Halo Objects survey of the Large Magellanic Cloud with infrared photometry from the Spitzer Space Telescope Surveying the Agents of a Galaxy's Evolution survey to create a data set of ~30,000 variable red sources. We photometrically classify these sources as being on the first ascent of the red ...

About half of the binary systems are close enough to each other for mass to be exchanged between them at some point in their evolution, yet the accretion mechanism in wind accreting binaries is not well understood. We study the dynamical effects of gravitational focusing by a binary companion on winds from late-type stars. In particular, we investigate the ...

Rapid rotation in field red giant stars is a relatively rare but well-studied phenomenon; here we investigate the potential role of planet accretion in spinning up these stars. Using Zahn's theory of tidal friction and stellar evolution models, we compute the decay of a planet's orbit into its evolving host star and the resulting transfer ...

At a distance of about only 100pc, Mira AB is the nearest symbiotic system containing an Asymptotic Giant Branch (AGB) star (Mira A), and a compact accreting companion (Mira B) at about 0.5" from Mira A. Symbiotic systems are interacting binaries with a key evolutionary importance as potential progenitors of a fraction of asymmetric Planetary Nebulae, and ...

The probability is evaluated that peculiar A and B stars show abundance anomalies from nuclear processes which occurred in companions. The mass accreted from supernova ejecta and the frequency of the accretion both in binary systems and in associations are evaluated. The results show that only one A or B star in a few thousand is likely to show abundance ...

Red giants stars are generally slow rotators, but a small fraction of them exhibit rapid rotation. The deposition of a planet's orbital angular momentum into the stellar envelope is one model that can account for this unusually rapid rotation. As the star evolves, it expands and fills the gap between itself and its planet. Eventually, the planet is near enough to cause stellar ...

The core accretion theory of planet formation has at least two fundamental problems explaining the origins of Uranus and Neptune: (1) dynamical times in the trans-saturnian solar nebula are so long that core growth can take >15 Myr and (2) the onset of runaway gas accretion that begins when cores reach 10 Earth masses necessitates a sudden gas ...

The four giant planets - Jupiter, Saturn, Uranus and Neptune - have common properties which make them very different from the terrestrial planets: located at large distances from the Sun, they have big sizes and masses but low densities; they all have a ring system and a large number of satellites. These common properties can be understood in the light of their formation ...

Using Ockham's razor as a guide, we have tried to find the simplest model for the formation of giant planets that can explain current observations of atmospheric composition. While this �top-down� approach is far from sufficient to define such models, it establishes a set of boundary conditions whose satisfaction is necessary. Using Jupiter as the prototype, we find that a ...

The supercritical wind theory of Papers II and III is applied to winds driven by accretion phenomena. An expression for the total luminosity LT is derived in terms of the accretion rate dotMT and injection radius r?. When applied specifically to accretion disks, the theory becomes the supercritical counterpart to standard subcritical ...

In order to explain the main characteristics of the observed population of extrasolar planets and the giant planets in the Solar system, we need to get a clear understanding of which are the initial conditions that allowed their formation. To this end we develop a semi-analytical model for computing planetary systems formation based on the core instability model for the gas ...

Recent Kepler observations revealed an abundance of 'hot' Earth-size to Neptune-size planets in the inner 0.02-0.2 au from their parent stars. We propose that at least some of these smaller planets are the remnants of massive giant planets that migrated inwards quicker than they could contract. We show that such disruptions occur if the young giant planet ...

Recent Kepler observations revealed an abundance of 'hot' Earth-size to Neptune-size planets in the inner 0.02-0.2 au from their parent stars. We propose that at least some of these smaller planets are the remnants of massive giant planets that migrated inwards quicker than they could contract. We show that such disruptions occur if the young giant planet ...

We present virial models for the global evolution of giant molecular clouds (GMCs). Focusing on the presence of an accretion flow and accounting for the amount of mass, momentum, and energy supplied by accretion and star formation feedback, we are able to follow the growth, evolution, and dispersal of individual GMCs. Our model clouds ...

KU Cyg is an eclipsing binary consisting of an F-type star accreting through a large accretion disk from a K5III red giant. Here we present the discovery of a 5 year dip around 1900 found from its 100 year DASCH light curve. It showed a ~0.5 mag slow fading from 1899 to 1903 and brightened back around 1904 on a relatively shorter ...

Gas giant planets undoubtedly form from the orbiting gas and dust disks commonly observed around young stars, and there are two principal mechanisms proposed for how this may occur. The core accretion plus gas capture model argues that a solid core forms first and then accretes gas from the surrounding disk once the core becomes ...

Extrasolar planet surveys have begun to detect planets in orbit around M dwarf stars. The frequency of gas giant planets around M dwarfs appears to be lower than that around G dwarfs, but it is not zero. Core accretion is too slow to form gas giant planets around M dwarfs. Disk instability is fast enough to form gas ...

PROF. GAMOW appears to agree with our view that accretion of hydrogen by the stars from the cosmical cloud would be important if the rate were sufficiently rapid to compensate the transmutation of hydrogen within the stars. He believes, however, that the accretion rate is too low for this to be happening in the case of a typical giant ...

We propose a two-component model consisting of a standard thin accretion disk and a hotter corona for 3U 1820--30, with the giant X-ray bursts originating in the inner (radiation-pressure dominated) region of the disk. Arguments in favor of and methods to test such a model are briefly discussed. Parameters of the bursting region are estimated, and an upper ...

This work presents a homogeneous derivation of atmospheric parameters and iron abundances for a sample of giant and subgiant stars which host giant planets, as well as a control sample of subgiant stars not known to host giant planets. The analysis is done using the same technique as for our previous analysis of a large sample of ...

We investigate the critical core mass and the envelope growth timescale, assuming grain-free envelopes, to examine how small cores are allowed to form gas giants in the framework of the core-accretion model. This is motivated by a theoretical dilemma concerning Jupiter formation: modelings of Jupiter's interior suggest that it contains a small ...

Symbiotic stars, in which material from a red-giant donor accretes onto or interacts with a compact companion, provide astrophysics with fascinating (relatively) nearby laboratories displaying phenomena such as astrophysical jets, shocks, accretion disks and colliding winds. Here we request a modest allotment of telescope time to image ...

We present J1145-0033, a candidate for the most distant (z=2.055) lobe-dominated giant radio quasar, with a projected linear size of 1.34 Mpc. This quasar has both FRII-type radio morphology and broad absorption lines in its optical spectrum. Some physical characteristics (e.g., black hole mass, accretion rate, equipartition magnetic field, energy density ...

We have computed the fate of exoplanet companions around main sequence stars to explore the frequency of planet ingestion by their host stars during the red giant branch evolution. Using published properties of exoplanetary systems combined with stellar evolution models and Zahn's theory of tidal friction, we modeled the tidal decay of the planets' orbits as their host stars ...

The positive correlation between planet detection rate and host star iron abundance lends strong support to the core accretion theory of planet formation. However, iron is not the most significant mass contributor to the cores of giant planets. Since giant planet cores grow from silicate grains with icy mantles, the likelihood of gas ...

Remnant planetesimals might have played an important role in reducing the orbital eccentricities of the terrestrial planets after their formation via giant impacts. However, the population and the size distribution of remnant planetesimals during and after the giant impact stage are unknown, because simulations of planetary accretion ...

Context: Evolved low-mass stars (0.8 ? M/M? ? 2.5) of a wide range of metallicity bear signatures of a non-standard mixing event in their surface abundances of Li, C, and N, and in their 12C/13C ratio. A Na overabundance has also been reported in some giants of open clusters but remains controversial. The cause of the extra-mixing has been attributed to thermohaline convection ...

Accretion left the terrestrial planets depleted in volatile components. Here I examine evidence for the hypothesis that the Moon and the Earth were essentially dry immediately after the formation of the Moon-by a giant impact on the proto-Earth-and only much later gained volatiles through accretion of wet material delivered from beyond ...

The equations describing the transport of suprathermal charged particles, electromagnetic radiation and neutrinos across accretion flows onto compact objects are solved analytically, the effects of shocks in the flow being included. These solutions are used in discussing three illustrative astrophysical examples: acceleration of cosmic rays, generation of spectral continua in ...

Symbiotic stars appear almost certainly to be interacting binaries with a cool giant losing mass from its wind or by Roche lobe overflow to a much more compact companion. The latter is thought to be usually a white dwarf, but may sometimes be a main sequence star and perhaps even a neutron star. Symbiotic stars go through activity phases, which are thought to be sometimes due ...

AG Dra is a symbiotic variable bearing a number of similarities to the suspected emitting components in RS Oph among which are an irradiated red giant mass donor, metal poor, similarly long orbital periods, a hot accreting white dwarf irradiating an optically thick bright accretion disk. Both objects have been counted among the yellow ...

A new combined rhenium-osmium- and platinum-group element data set for basalts from the Moon establishes that the basalts have uniformly low abundances of highly siderophile elements. The data set indicates a lunar mantle with long-term, chondritic, highly siderophile element ratios, but with absolute abundances that are over 20 times lower than those in Earth's mantle. The results are consistent ...

In a close binary system or in a dense cloud, gas may be accreted onto a carbon-oxygen white dwarf and will be processed into helium by hydrogen burning in an accreted envelope. As a result, a helium zone grows in mass, and a helium shell flash takes place just as in cores of red giant stars. Properties of such helium shell flashes are ...

Considerations related to the angular momentum of the earth-moon system have led Ward and Cameron (1978) to the suggestion of a collisional origin of the moon. The required projectile would be about the mass of Mars (i.e., about 0.1 earth masses). The possibility has been considered that both the proto-earth and the projectile would be remnants of the formation of giant ...

The formation of the giant planets seems to be best explained by accretion of planetesimals to form massive cores, which in the case of Jupiter and Saturn were able to capture nebular gas. However, the timescale for accretion of such cores has been a problem. Accretion in the outer solar system differs ...

We track the coevolution of supermassive black holes (SMBHs) and their host galaxies through cosmic time. The calculation is embedded in the GALFORM semi-analytic model which simulates the formation and evolution of galaxies in a cold dark matter (CDM) universe. The black hole (BH) and galaxy formation models are coupled: during the evolution of the host galaxy, hot and cold gas are added to the ...

The water content and habitability of terrestrial planets are determined during their final assembly, from perhaps 100 1,000-km "planetary embryos " and a swarm of billions of 1-10-km "planetesimals. " During this process, we assume that water-rich material is accreted by terrestrial planets via impacts of water-rich bodies that originate in the outer asteroid region. We ...

The origin of ultra-compact binaries composed of a neutron star and a low-mass (about 0.06 solar mass) white dwarf is considered. Taking account of the systemic losses of mass and angular momentum, it was found that a serious difficulty exists in the scenarios which involve tidal captures of a normal star (a main sequence star or a red giant) by a neutron star. This difficulty ...

The properties of the AL Vel binary system, a Zeta Aur system containing a B dwarf and a bright K0 giant, are reviewed with reference to IUE observations of its atmospheric eclipse and eclipse of the accretion disk around the B-dwarf component. It is found that the conditions in the chromosphere are rather similar to those in the Zeta Aur supergiants, once ...

As a star evolves off the Main Sequence, it endures major structural changes that are capable of determining the fate of the planets orbiting it. Throughout its evolution along the Red Giant Branch, the star increases its radius by two orders of magnitude. Later, during the Asymptotic Giant Branch, it loses most of its initial mass. Finally, during the ...

Energy release by the evaporation of neutrons from nuclei in red giants with degenerate neutron cores is analyzed. Stellar contraction resulting from accretion onto a neutron star is examined, and thermonuclear fusion leading to the formation of magnesium is considered. It is shown that evaporation of neutrons initially transforms 1.927 MeV/n of energy ...

H I gas has been found between a dwarf irregular and the giant elliptical galaxy NGC 4472 in the Virgo Cluster. The H I deficiency of the dwarf itself suggests that the H I seen has been removed from the dwarf by either tidal stripping or the sweeping effect of the hot gaseous halo, which is known from X-ray data to be surrounding the elliptical galaxy. Hence it is possible ...

Planetary migration poses a serious problem for theories of planet formation. In the core accretion model, giant planets form a solid core of roughly 10 Earth masses by accumulating from planetesimals. The core subsequently accretes a gaseous envelope. Cores generate and interact with spiral density waves in the nebula gas, moving ...

Interior to the gaseous envelopes of Saturn, Uranus, and Neptune, there are high-density cores with masses larger than 10 Earth masses. According to the conventional sequential accretion hypothesis, such massive cores are needed for the onset of efficient accretion of their gaseous envelopes. However, Jupiter's gaseous envelope is more massive and its core ...

Interior to the gaseous envelopes of Saturn, Uranus, and Neptune, there are high-density cores with masses larger than 10 Earth masses. According to the conventional sequential accretion hypothesis, such massive cores are needed for the onset of efficient accretion of their gaseous envelopes. However, Jupiter's gaseous envelope is more massive and ...

Gennaro D'Angelo (gennaro.dangelo@nasa.gov) NASA Ames Research Center and University of California, Santa Cruz Planetesimal Accretion during Runaway Gas Growth of Giant Planets The presence of regular and irregular satellites around Jupiter and Saturn likely involved accretion of planetesimals from a dissipating Solar Nebula. A gas ...

We present an analysis of high-resolution spectra of three core-helium-burning 'clump' stars and two first ascent giants in the open cluster IC 4651. Atmospheric parameters (Teff, log g, vt and [Fe/H]) were determined in our previous study by Carretta et al. In this study, we present abundances of C, N, O and up to 24 other chemical ...

The Hipparcos orbiting observatory has revealed a large number of helium-core-burning �clump� stars in the Galactic field. These low-mass stars exhibit signatures of extra mixing processes that require modelling beyond the first dredge-up of standard models. The 12C/13C ratio is the most robust diagnostic of deep mixing because it is insensitive to the adopted stellar parameters. In this paper ...

With the ever increasing number of extrasolar planets being discovered (373 as of 8/13/09 quoted by The Extrasolar Planets Encyclopedia: exoplanet.eu) and the recognition of their diverse nature it is very important to understand the formation processes of the gas giant planets. The core accretion model has successfully explained many features of the ...

A supermassive black hole in the nucleus of an elliptical galaxy at the centre of a cool-core group or cluster of galaxies is immersed in hot gas. Bondi accretion should occur at a rate determined by the properties of the gas at the Bondi radius and the mass of the black hole. X-ray observations of massive nearby elliptical galaxies, including M87 in the Virgo cluster, ...

A supermassive black hole in the nucleus of an elliptical galaxy at the centre of a cool-core group or cluster of galaxies is immersed in hot gas. Bondi accretion should occur at a rate determined by the properties of the gas at the Bondi radius and the mass of the black hole. X-ray observations of massive nearby elliptical galaxies, including M87 in the Virgo cluster, ...

We provide a brief review of thermohaline physics and why it is a candidate extra mixing mechanism during the red giant branch (RGB). We discuss how thermohaline mixing (also called delta mu mixing) during the RGB owing to {3He} burning, is more complicated than the operation of thermohaline mixing in other stellar contexts (such as following accretion ...

The explanation that lunar origin involved giant impacts remains attractive. Large planetesimals are consistent with current accretion models, and may have been widely scattered in the early solar system. Their existence is a reasonable, assumption in Moon origin models. Isotopic data require the Moon's formation primarily from local material ...

In the core accretion model, giant planets are assumed to form around a growing core of condensible materials. As this core grows, it attracts an envelope of gas and dust from the surrounding nebula. Up to the so-called critical core mass, this evolution is quasi static. By studying all allowed equilibria that are the progenitors of mature planets, we ...

As part of its Ultraviolet Studies of Astronomical Sources the Smithsonian Astrophysical Observatory for the period 1 Feb. 1985 to 31 July 1985 observed the following: the Cygnus Loop; oxygen-rich supernova remnants in 1E0102-72; the Large Magellanic Cloud supernova remnants; P Cygni profiles in dwarf novae; soft X-ray photoionization of interstellar gas; spectral variations in AM Her stars; the ...

by a non negligible factor. 3.2. Giant planets in Jovian�like primordial orbits The competing hypothesis for the origin of Jovian�type planets is the accumula� tion of a massive core that accretes gas from the nebula the search for planets around main se� quence stars other than the Sun has experienced rapid progress but

The alkali depletion is not a unique characteristic of the moon, but is common to eucrites, angrites, and the earth. Because the moon and the earth are depleted in more volatile Pb in a similar degree to both chondrites and achondrites, it is hard to assume that alkali depletion was caused by vaporization loss during the giant impact event. Alkali and volatile depletion might ...

The origin of the moon is examined in the context of theories of planetary accretion and of siderophile element abundances inferred for the upper mantles of the earth, moon, and shergottite parent body (SPB = Mars.). The lunar origin hypotheses examined are collisional ejection in a giant imact, and coaccretion from a circumterrestrial disk of ...

Protoatmospheres and surface environment of terrestrial protoplanets during the oligarchic accretion phase and the giant impacts phase are discussed from theoretical points of view. Mars-sized protoplanets form during the stage of the oligarchic growth. Since protoplanets are formed from more or less `local' planetesimals, the surface environment of the ...

We show that the amount of energy produced by a thermal pulse corresponds to the transition between two different eigenstates, one accretion-controlled and the other burning-controlled. It is the coupling between the large amount of energy required to perform such a switch and the fast injection of this energy in the star (a consequence of a thermal instability caused by the ...

A widely accepted model for the origin of the Earth and Moon has been a somewhat specific giant impact scenario involving an impactor to proto-Earth mass ratio of 3:7, occurring 50-60 Ma after T(sub 0), when the Earth was only half accreted, with the majo...

A new tectonic model, postulating the growth of giant subduction-accretion complexes along a single magmatic arc now found contorted between Siberia and Baltica, shows that Asia grew by 5.3 million square kilometres during the Palaeozoic era. Half of this growth may have occurred by the addition of juvenile crust newly extracted from the mantle, supporting ...

We modeled the microphysics of grain growth and sedimentation in the outer radiative part of the envelope of a protoplanet forming in the core accretion scenario of tet{hubickyj05}. We find that the resultant opacity is almost always lower than that generally assumed for interstellar grains, but is higher, in some parts of the envelope, than the low opacities assumed by ...

We have obtained millimeter-wavelength photometry, high-resolution optical spectroscopy, and adaptive optics near-infrared imaging for a sample of 26 Spitzer-selected transition circumstellar disks. All of our targets are located in the Ophiuchus molecular cloud (d {approx} 125 pc) and have spectral energy distributions (SEDs) suggesting the presence of inner opacity holes. We use these ...

Symbiotic stars are long-period interacting binaries composed of an evolved cool giant and a hot and luminous companion - in most cases a wind-accreting post-AGB star - surrounded by an ionized nebula. The nature of the cool giant plays a key role in the symbiotic phenomenon: it constrains the size of the binary, which must have enough ...

Doppler surveys have shown that more massive stars have significantly higher frequencies of giant planets inside ~3 AU than lower mass stars, consistent with giant planet formation by core accretion. Direct imaging searches have begun to discover significant numbers of giant planet candidates around stars with ...

We review recent theoretical progress aimed at understanding the formation and the early stages of evolution of giant planets, low-mass stars, and brown dwarfs. Calculations coupling giant planet formation, within a modern version of the core accretion model that includes planet migration and disk evolution, and subsequent evolution ...

Direct imaging searches have begun to detect planetary and brown dwarf companions and to place constraints on the presence of giant planets at large separations from their host star. This work helps to motivate such planet searches by predicting a population of young giant planets that could be detectable by direct imaging campaigns. Both the classical ...

I suggest the existence of an extended zone above the surface of asymptotic giant branch (AGB), as well as similar stars experiencing high mass-loss rates. In addition to the escaping wind, in this zone there are parcels of gas that do not reach the escape velocity. These parcels of dense gas rise slowly and then fall back. The wind and bound gas exist simultaneously to ...

Most of the mass of a gaseous giant planet is acquired from the proto-planetary disk, in which the planet forms, during a phase of envelope collapse. Rapid contraction of the envelope begins when the mass of the envelope is of the same order of the solid core mass. During this phase, a giant planet accretes gas at a rate that is ...

Properties of white dwarfs which are accreting hydrogen-rich matter at rates in the range 1.5 x 10/sup -9/ to 2.5 x 10/sup -7/ M/sub sun/ yr/sup -1/ are investigated in several approximations. Steady-burning models, in which matter is processed through nuclear-burning shells as rapidly as it is accreted, provide a framework for understanding the properties ...

A quarter of DA white dwarfs are metal polluted, yet elements heavier than helium sink down through the stellar atmosphere on time-scales of days. Hence, these white dwarfs must be the currently accreting material containing heavy elements. Here we consider whether the scattering of comets or asteroids from an outer planetary system, following stellar mass-loss on the ...

We present an abundance analysis based on high-resolution spectra of eight stars selected to span the full range in metallicity in the Draco dwarf spheroidal (dSph) galaxy. We find that [Fe/H] for the sample stars ranges from -1.5 to -3.0 dex. Combining our sample with previously published work for a total of 14 luminous Draco giants, we show that the abundance ratios [Na/Fe], ...

We use two-dimensional hydrodynamic simulations of viscous disks to examine whether dynamically interacting multiple giant planets can explain the large gaps (spanning over one order of magnitude in radius) inferred for the transitional and pre-transitional disks around T Tauri stars. In the absence of inner disk dust depletion, we find that it requires three to four ...

We present the results of hydrodynamic simulations of the formation and subsequent orbital evolution of giant planets embedded in a circumbinary disc. We assume that a 20 earth masses core has migrated to the edge of the inner cavity formed by the binary where it remains trapped by corotation torques. This core is then allowed to accrete gas from the disc, ...

Neptune is the outermost of the four giant planets in our solar system. The region in which Neptune orbits has longer dynamical time scales and probably had a lower surface mass density of solids than zones closer to the Sun. Both of these properties suggest that Neptune took significantly longer to accrete than did the other giant ...

The satellite systems of Jupiter and Saturn are thought to have formed from circumplanetary disks that surrounded these planets during their accretion. However, large satellites are susceptible to loss from rapid type I orbital decay due to strong disk torques. It has been proposed [1,2] that the current satellites are in fact the last survivors of continuing cycles of ...

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 ...

Aims: We present the results of hydrodynamic simulations of the growth and orbital evolution of giant planets embedded in a protoplanetary disk with a dead-zone. The aim is to examine to what extent the presence of a dead-zone affects the rates of mass accretion and migration for giant planets. Methods: We performed 3D numerical ...

A leading theory for giant planet formation involves the accretion of a solid core, probably ice-rich, that in turn accretes a massive mantle of hydrogen-helium gas from a primordial disk. The relative timing of core formation and disappearance of nebular gas in a few millions of years is critical; the correlation between heavy ...

New numerical simulations of the evolution and formation of Jupiter were computed. Earlier studies of the core instability model demonstrated that it was possible to form Jupiter with a solid core of 10 to 30 M? within the lifetime of the protoplanetary disk (about 107 years). However, recent interior models of Jupiter suggest a core mass of about 5 M? . We examine the effects of adjusting ...

We use two-dimensional hydrodynamic simulations of viscous disks to examine whether dynamically-interacting multiple giant planets can explain the large gaps inferred for the transitional and pre-transitional disks around T Tauri stars. In the absence of inner disk dust depletion, we find that it requires three to four giant planets to open up large enough ...

The recent discoveries of massive planets on ultra-wide orbits of HR 8799 and Fomalhaut present a new challenge for planet formation theorists. Our goal is to figure out which of three giant planet formation mechanisms-core accretion (with or without migration), scattering from the inner disk, or gravitational instability-could be responsible for Fomalhaut ...

Behavior of volatile material during accretion of terrestrial planets is discussed from theoretical point of view. The recent planetary formation theory suggests two stages of planetary formation; the stage of oligarchic growth (e.g., Kokubo and Ida, 1998) followed by the stage of giant impacts (e.g., Chambers and Wetherill, 1998). Mars-sized protoplanets ...

Small differences in the ratio of neodymium-142 to neodymium-144 in early formed mantle reservoirs in planetary bodies are the result of in situ decay of the extinct radionuclide samarium-146 and can be used to constrain early planetary differentiation and therefore the time scale of planetary accretion. The martian meteorite Nakhla (approximately 1.3 billion years old), the ...

We isolate a sample of 43 upper red giant branch stars in the extreme outer halo Galactic globular cluster (GC) NGC 2419 from two Keck/DEIMOS slitmasks. The probability that there is more than one contaminating halo field star in this sample is extremely low. Analysis of moderate-resolution spectra of these cluster members, as well as of our Keck/HIRES high-resolution spectra ...

The space-time around Neutron Stars is indeed an extreme environment. Whether they are in accreting binary systems, isolated or in non-accreting binaries (perhaps with another Neutron Star), Neutron Stars provide a window onto physical processes not accessible by other means. In particular, the study of their time variability: pulsations, quasi-periodic ...

The stellar initial mass function (IMF) is determined by a process of fragmentation and accretion in the opaque, dense center of a giant molecular cloud. This environment effectively traps radiation from newborn stars, and the interaction between the gas and the radiation is the dominant feature controlling the thermodynamics and in some extreme cases the ...

Type Ia supernovae are important cosmological distance indicators. Each of these bright supernovae supposedly results from the thermonuclear explosion of a white dwarf star that, after accreting material from a companion star, exceeds some mass limit, but the true nature of the progenitor star system remains controversial. Here we report the spectroscopic detection of ...

We will present Chandra observations of 4 giant elliptical galaxies:NGC1399,NGC1404,NGC4472 and NGC4636. We have determined the spectrum with position deriving temperature and abundance profiles, cooling times and mass accretion rates. We place strong upper limits on the presence of a central point source strongly bounding accretion ...

The neutron star crust, the 1 kilometer region on the surface composed of nuclei and superfluid neutrons, is the physical location of the majority of the phenomena observed in neutron stars. The composition of the crust is a fundamental input for the evolution of isolated and accreting neutron stars, and is important for the description of rp-process nucleosynthesis, ...