共查询到20条相似文献,搜索用时 46 毫秒
1.
Elmar Körding 《Space Science Reviews》2014,183(1-4):149-161
Accretion is a ubiquitous phenomenon—it is seen in sources ranging from young stars to accreting supermassive black holes in the centres of galaxies. Here, we present the known empirical connections between stellar mass X-ray binaries and active galactic nuclei. We argue that this implies that both the accretion disc and the jet are scale invariant with respect to the black hole mass. Finally, we show that also accretion discs and jets in sources with a different accretor can be connected empirically to accreting black holes, hinting towards a common mechanism of accretion in all sources. 相似文献
2.
Yann Alibert Christoph Mordasini Olivier Mousis Willy Benz 《Space Science Reviews》2005,116(1-2):77-95
We present models of giant planet formation, taking into account migration and disk viscous evolution. We show that migration
can significantly reduce the formation timescale bringing it in good agreement with typical observed disk lifetimes. We then
present a model that produces a planet whose current location, core mass and total mass are comparable with the one of Jupiter.
For this model, we calculate the enrichments in volatiles and compare them with the one measured by the Galileo probe. We
show that our models can reproduce both the measured atmosphere enrichments and the constraints derived by Guillot et al. (2004), if we assume the accretion of planetesimals with ices/rocks ratio equal to 4, and that a substantial amount of CO2 was present in vapor phase in the solar nebula, in agreement with ISM measurements. 相似文献
3.
We review how the single degenerate models for Type Ia supernovae (SNe Ia) works. In the binary star system of a white dwarf (WD) and its non-degenerate companion star, the WD accretes either hydrogen-rich matter or helium and undergoes hydrogen and helium shell-burning. We summarize how the stability and non-linear behavior of such shell-burning depend on the accretion rate and the WD mass and how the WD blows strong wind. We identify the following evolutionary routes for the accreting WD to trigger a thermonuclear explosion. Typically, the accretion rate is quite high in the early stage and gradually decreases as a result of mass transfer. With decreasing rate, the WD evolves as follows: (1) At a rapid accretion phase, the WD increase its mass by stable H burning and blows a strong wind to keep its moderate radius. The wind is strong enough to strip a part of the companion star’s envelope to control the accretion rate and forms circumstellar matter (CSM). If the WD explodes within CSM, it is observed as an “SN Ia-CSM”. (X-rays emitted by the WD are absorbed by CSM.) (2) If the WD continues to accrete at a lower rate, the wind stops and an SN Ia is triggered under steady-stable H shell-burning, which is observed as a super-soft X-ray source: “SN Ia-SSXS”. (3) If the accretion continues at a still lower rate, H shell-burning becomes unstable and many flashes recur. The WD undergoes recurrent nova (RN) whose mass ejection is smaller than the accreted matter. Then the WD evolves to an “SN Ia-RN”. (4) If the companion is a He star (or a He WD), the accretion of He can trigger He and C double detonations at the sub-Chandrasekhar mass or the WD grows to the Chandrasekhar mass while producing a He-wind: “SN Ia-He CSM”. (5) If the accreting WD rotates quite rapidly, the WD mass can exceed the Chandrasekhar mass of the spherical WD, which delays the trigger of an SN Ia. After angular momentum is lost from the WD, the (super-Chandra) WD contracts to become a delayed SN Ia. The companion star has become a He WD and CSM has disappeared: “SN Ia-He WD”. We update nucleosynthesis yields of the carbon deflagration model W7, delayed detonation model WDD2, and the sub-Chandrasekhar mass model to provide some constraints on the yields (such as Mn) from the comparison with the observations. We note the important metallicity effects on 58Ni and 55Mn. 相似文献
4.
We computed the evolution through case A mass transfer for 8 systems with mass of the primary equal to 3 and 5 M0, mass ratios 0.7 and 0.9, and different periods. To this we added similar results from Packet (1988) for Mi = 9 M0, qi = 0.6, Pi = 1.62 d.During the mass transfer two competing mechanisms in the gainer decide on the evolution of the system: the rejuvenation of this star as the increasing convective core mixes fresh hydrogen into the inner regions, and the acceleration of nuclear burning, responding to the increasing mass.In all the cases the net result is a faster decrease of the central hydrogen content compared to the mass losing star. The secondary fills its own critical Roche lobe and reversed mass transfer starts.From our results and those of Nakamura and Nakamura (1984), we find that reversed mass transfer occurs after core hydrogen burning of the secondary (case A1B2) approximately for periods larger than 1 d (M1i = 3 M0) to 2 d (M1i = 13.4 M0). For smaller periods this happens before the gainer ends its core hydrogen burning (case A1A2). 相似文献
5.
Ken'ichi Nomoto 《Space Science Reviews》1980,27(3-4):563-570
Supernova mechanisms in accreting white dwarfs (WDs) are presented, i.e., the carbon deflagration as a plausible mechanism for producing Type I supernovae and electron captures to form quiet supernovae leaving neutron stars. These outcomes depend on accretion rate of helium, initial mass and composition of the WD. The various types of hydrogen shell-burning in the presupernova stage are also discussed.on leave from Department of Physics, Ibaraki University, Japan. 相似文献
6.
J. P. De Greve 《Space Science Reviews》1986,43(1-2):139-210
The present knowledge on the evolution of semidetached systems is reviewed. Characteristics of observed systems are discussed and general properties tested by the behaviour of theoretical models. New models of mass accreting companion stars are computed. The accretion phase is divided into a fast and slow phase with an accretion rate depending on the initial mass of the mass losing star and on the initial mass ratio, assuming the systems are undergoing a case B of mass transfer. The results are compared with observed systems with masses of the gainers located within the theoretical range. Up to now no computations exist for the evolution of medium mass close binaries including overshooting of the convective core. However some of the influences of extended convective mixing on the interaction of close binaries are investigated. A larger probability for the occurrence of case A of mass exchange and a larger remnant mass at the end of the process are the most important results. Finally the investigation into the origin of individual systems (in mass, mass ratio and period) is discussed, showing that progress both in observations and in theoretical models result in a more detailed and more restricted determination of the initial parameters of the individual systems.Research associate, NFWO, Belgium. 相似文献
7.
In this article, we will briefly review the current empirical understanding of the relation between accretion state and outflows in accreting stellar mass black holes. The focus will be on the empirical connections between X-ray states and relativistic (‘radio’) jets, although we are now also able to draw accretion disc winds into the picture in a systematic way. We will furthermore consider the latest attempts to measure/order jet power, and to compare it to other (potentially) measurable quantities, most importantly black hole spin. 相似文献
8.
We review results about protoplanetary disk models, protoplanet migration and formation of giant planets with migrating cores.
We first model the protoplanetary nebula as an α–accretion disk and present steady state calculations for different values
of α and gas accretion rate through the disk. We then review the current theories of protoplanet migration in the context
of these models, focusing on the gaseous disk–protoplanet tidal interaction. According to these theories, the migration timescale
may be shorter than the planetary formation timescale. Therefore we investigate planet formation in the context of a migrating
core, considering both the growth of the core and the build–up of the envelope in the course of the migration.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Vytenis M. Vasyliunas 《Space Science Reviews》1979,24(4):609-634
A wide class of galactic X-ray sources are believed to be binary systems where mass is flowing from a normal star to a companion that is a compact object, such as a neutron star. The strong magnetic fields of the compact object create a magnetosphere around it. We review the theoretical models developed to describe the properties of magnetospheres in such accreting binary systems. The size of the magnetosphere can be estimated from pressure balance arguments and is found to be small compared to the over-all size of the accretion region but large compared to the compact object if the latter is a neutron star. In the early models the magnetosphere was assumed to have open funnels in the polar regions, through which accreting plasma could pour in. Later, magnetically closed models were developed, with plasma entry made possible by instabilities at the magnetosphere boundary. The theory of plasma flow inside the magnetosphere has been formulated in analogy to a stellar wind with reversed flow; a complicating factor is the instability of the Alfvén critical point for inflow. In the case of accretion via a well-defined disk, new problems of magnetospheric structure appear, in particular the question to what extent and by what process the magnetic fields from the compact object can penetrate into the accretion disk. Since the X-ray emission is powered by the gravitational energy released in the accretion process, mass transfer into the magnetosphere is of fundamental importance; the various proposed mechanisms are critically examined.Proceedings of the NASA/JPL Workshop on the Physics of Planetary and Astrophysical Magnetospheres. 相似文献
10.
The environments of both hot and cool stars are the sites of highly dynamic processes involving motion of gas and plasma in winds, flows across shocks, plasma motions in closed magnetic fields, or streams along magnetospheric accretion funnels. X-ray spectroscopy has opened new windows toward the study of these processes. Kinematics are evident in line shifts and line broadening, and also more indirectly through the analysis and interpretation of density-sensitive lines. In hot stellar winds, expanding-wind kinematics are directly seen in broadened lines although the broadening has turned out to often be smaller than anticipated, and some lines are so narrow that coronal models have been revived. Although X-ray spectra of cool stars have shown line shifts and broadening due to the kinematics of the entire corona, e.g., in binary systems, intrinsic mass motions are challenging to observe at the presently available resolution. Much indirect evidence for mass motion in magnetic coronae is nevertheless available. And finally, spectral diagnostics has also led to a new picture of X-ray production in accreting pre-main sequence stars where massive accretion flows collide with the photospheric gas, producing shocks in which gas is heated to high temperatures. We summarize evidence for the above mechanisms based on spectroscopic data from XMM-Newton and Chandra. 相似文献
11.
Thomas J. Maccarone 《Space Science Reviews》2014,183(1-4):101-120
In this chapter, I present a summary of observational tests of the basic picture of disk accretion. An emphasis is placed on tests relevant to black holes, but many of the fundamental results are drawn from studies of other classes of systems. Evidence is discussed for the basic structures of accretion flows. The cases of systems with and without accretion disks are discussed, as is the evidence that disks actually form. Also discussed are the hot spots where accretion streams impact the disks, and the boundary layers in the inner parts of systems where the accretors are not black holes. The nature of slow, large amplitude variability is discussed. It is shown that some of the key predictions of the classical thermal-viscous ionization instability model for producing outbursts are in excellent agreement with observational results. It is also show that there are systems whose outbursts are extremely difficult to explain without invoking variations in the rate of mass transfer from the donor star into the outer accretion disk, or tidally induced variations in the mass transfer rates. Finally, I briefly discuss recent quasar microlensing measurements which give truly independent constraints on the inner accretion geometry around black holes. 相似文献
12.
Katharina Lodders 《Space Science Reviews》2000,92(1-2):341-354
The oxygen isotope systematics in planetary and nebular matter are used to constrain the types of nebular material accreted
to form a planet. The basic assumption of this model is that the mean oxygen isotopic composition of a planet is determined
by the weighted mean oxygen isotopic composition of nebular matter accreted by the planet. Chondrites are taken as representatives
of nebular matter. The chemical composition (which determines core size, mantle oxidation state, density, moment of inertia)
of a planet results from the weighted mean compositions of the accreted nebular material, once the mass fractions of the different
types of accreting matter are known. Here some results for Earth, Moon, Mars, and Vesta are discussed. The model implies that
loss of volatile elements, such as alkalis and halogens, occurs during accretion and early planetary differentiation (e. g., by catastrophic impacts). The possible depletion mechanisms of moderately volatile elements are discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
14.
Frank Verbunt 《Space Science Reviews》1982,32(4):379-404
This review presents an introduction to the theory of accretion disks. After explaining the importance of accretion disks in stellar X-ray sources, it considers observational and theoretical indications of the formation of accretion disks in close binary systems. The simple Shakura and Sunyaev model and its problems are discussed. A survey of other models that try to improve upon this model is given (in Table III), and critically discussed. 相似文献
15.
N. Labrosse P. Heinzel J.-C. Vial T. Kucera S. Parenti S. Gunár B. Schmieder G. Kilper 《Space Science Reviews》2010,151(4):243-332
This review paper outlines background information and covers recent advances made via the analysis of spectra and images of
prominence plasma and the increased sophistication of non-LTE (i.e. when there is a departure from Local Thermodynamic Equilibrium) radiative transfer models. We first describe the spectral
inversion techniques that have been used to infer the plasma parameters important for the general properties of the prominence
plasma in both its cool core and the hotter prominence-corona transition region. We also review studies devoted to the observation
of bulk motions of the prominence plasma and to the determination of prominence mass. However, a simple inversion of spectroscopic
data usually fails when the lines become optically thick at certain wavelengths. Therefore, complex non-LTE models become
necessary. We thus present the basics of non-LTE radiative transfer theory and the associated multi-level radiative transfer
problems. The main results of one- and two-dimensional models of the prominences and their fine-structures are presented.
We then discuss the energy balance in various prominence models. Finally, we outline the outstanding observational and theoretical
questions, and the directions for future progress in our understanding of solar prominences. 相似文献
16.
Alex N. Halliday 《Space Science Reviews》2000,92(1-2):355-370
Models for the mechanisms of accretion of the terrestrial planets are re-examined using the experimental technique of high-precision
isotope ratio mass spectrometry of tungsten (W). The decay of 182Hf to 182W (via 182Ta) provides a new kind of radiometric chronometer of planet formation processes. Hafnium and W, the parent and daughter trace
elements, are highly refractory; however, Hf is lithophile and strongly partitioned into the silicate portion of a planet,
whereas W is moderately siderophile and preferentially partitioned into a coexisting metallic phase. More than 90% of terrestrial
W has gone into the Earth's core during its formation. The residual silicate portion, the Earth's primitive mantle, has a
Hf/W ratio in the range 10−40, an order of magnitude higher than chondritic (∼1.3). Tungsten isotopic data for the Earth and
the Moon suggest that we can date a major event of planet formation: The Moon formed about 50 Myrs after the start of the
solar system, providing strong support for the Giant Impact Theory of lunar origin. Recent simulations of this event imply
that the Earth was probably only half formed at the time. From this we can deduce the planetary accretion rate. Tungsten isotope
data for Mars provide evidence of a much shorter accretion interval, perhaps as little as 10 Myrs, but the rates for the Earth
over the same time interval could have been comparable. The large W isotopic heterogeneities on Mars could only have been
produced within the first 30 Myrs of the solar system. Large-scale mixing, e.g. from convective overturn, as is thought to drive the Earth's plates, must be absent from Mars.
Limitations of the method such as 1) cosmogenic 182Ta effects on lunar samples, 2) incomplete mixing of debris to cause W isotope heterogeneity on the Moon, and 3) initial 182Hf/180Hf heterogeneities of the early solar system are critically discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
Astrophysical limitations do not exclude the possibility of some number of dark matter primordial Black Holes (BH) being seeded in the interiors of the Earth at the epoch of planet condensation in the young Solar System. We show that limitations on the neutrino radiation due to the BH quantum evaporation and accretion growth of BH mass completely forbid the existence of primordial BH of any mass in the Earth. 相似文献
18.
19.
Multiwavelength variability data, combined with spectral-timing analysis techniques, provides information about the causal relationship between different physical components in accreting black holes. Using fast-timing data and long-term monitoring, we can probe the behaviour of the same components across the black hole mass scale. In this chapter we review the observational status of multiwavelength variability in accreting black holes, from black hole X-ray binaries to AGN, and consider the implications for models of accretion and ejection, primarily considering the evidence for accretion disc and jet variability in these systems. We end with a consideration of future prospects in this quickly-developing field. 相似文献