共查询到20条相似文献，搜索用时 954 毫秒
1.
叙述了与Astrod工程有关的相对论天体力学基础内容。包括相对论天体力学、广义相对论基本原理、PPN方法体系、PPN多体问题、PPN二体问题。高阶PN二体问题等 相似文献
2.
《New Astronomy Reviews》2002,46(2-7):387-391
We have applied an effective numerical scheme for cosmic-ray transport to 3D MHD simulations of jet flow in radio galaxies (see the companion paper by Jones et al. herein). The marriage of relativistic particle and 3D magnetic field information allows us to construct a rich set of ‘synthetic observations’ of our simulated objects. The information is sufficient to calculate the ‘true’ synchrotron emissivity at a given frequency using explicit information about the relativistic electrons. This enables us to produce synchrotron surface-brightness maps, including polarization. Inverse-Compton X-ray surface-brightness maps may also be produced. First results intended to explore the connection between jet dynamics and electron transport in radio lobes are discussed. We infer lobe magnetic field values by comparison of synthetically observed X-ray and synchrotron fluxes, and find these ‘inverse-Compton’ fields to be quite consistent with the actual RMS field averaged over the lobe. The simplest minimum energy calculation from the synthetic observations also seems to agree with the actual simulated source properties. 相似文献
3.
Principles of the theory of turbulence in relativistic cosmology are developed. By averaging Einstein's equations over stochastic fields a self-consistent system of equations is obtained which describes statistically: (1) the influence of the turbulence on the ‘basic state of the Universe (the background) on which the turbulence develops; (2) the behaviour of the turbulence on the background ‘distorted’ by it. By means of a qualitative study of exact equations in the region of a strong turbulence at an early stage of cosmological expansion conditions of the absence of singularity are found and the possibility of stationary solutions in the homogeneous, isotropic, on the average, Universe (the cosmological constantA=0) is shown. The rate of cosmological expansion increases if the energy density of the turbulence is positive, and decreases if it is negative. The latter alternative takes place if the absolute value of the energy density of excitations, which will change into potential motions in the future, exceeds the energy density of the remaining part of the turbulence. 相似文献
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M. T. Crosta A. Vecchiato F. de Felice M. G. Lattanzi B. Bucciarelli 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):209-218
In this article we outline the structure of a general relativistic astrometric model which has been developed to deduce the position and proper motion of stars from 1 µarcsecond optical observations made by an astrometric satellite orbiting around the Sun. The basic assumption of our model is that the Solar System is the only source of gravity, hence we show how we modeled the satellite observations in a many-body perturbative approach limiting ourselves to the order of accuracy of (v/c)2. The microarcsecond observing scenario outlined is that for the GAIA astrometric mission. 相似文献
6.
The special and general relativistic corrections for the basic radiointerferometric observables —time-delay and fringe frequency — are studied with an accuracy of the order of 5×10?10 (‘post-Newtonian approximation’). 相似文献
7.
C. D. Andriesse 《Astrophysics and Space Science》1983,89(2):401-406
By use of the fluctuation theory the mass of the massive stars can be calculated from the ‘observed’ luminosity, effective temperature and mass-loss rate. These masses differ from those obtained by fits to the ‘conventional’ evolution-tracks and they are used to construct alternative evolution-tracks. 相似文献
8.
Using a model of relativistic collision between two media and based on the theory of shock waves in an ideal relativistic fluid, we calculate in detail, the main parameters at the Initial stage of the formation of radio component sources, including the separation velocity and the travelling speed of the shock. The evolution of the hot spot as it moved from within the galaxy to a quasi-steady state in the intergalactic space is discussed qualitatively. Lastly, the parameters in the quasi-steady state are approximately evaluated using the formulae for strong shocks. The results obtained are in overall agreement with observations. 相似文献
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M. Yokosawa 《Astrophysics and Space Science》1982,83(1-2):335-366
Dynamical evolution of a relativistic beam ejected from a galactic centre is studied using the similarity method for the relativistic winds flowing through channels. The expansion phase is divided into two stages: A relativistic expansion and a non-relativistic expansion stage. By the dimensional analysis for a relativistic wind, the propagation law of the expanding wave front is obtained. When the front moves relativistically, the density of the ambient matter observed in the co-moving frame of the front increases by the Lorentz contraction and mass increment, and the propagation law obtained in the classical theory is modified by these relativistic effects. On the basis of a perturbation method, a new similarity method for a relativistic flow whose front velocity is varing with the expansion is presented. The flow structures of the relativistic wind are given. With the expansion of a beam, the inward-facing shock wave is more separated from the front of the outward-expanding shock wave and its shock strength becomes stronger than that of the outward-expanding shock wave when the ejected beam consists of energetic particles. The evolutions of the extragalactic double sources are considered. The relative position of the hot spot in the radio map is presented at each stage of the expansion and discussed with the observational radio maps. The time variation of the radio emission is predicted. 相似文献
11.
Osamu Kaburaki 《Astrophysics and Space Science》1983,92(1):113-134
The structure of the corotating region, which forms an inner portion of a stellar magnetosphere, is reconsidered in a quasi-neutral case by taking into account the inertial effects of electrons as well as that of ions up to the first order in their mass ratio (δ=m?/m+). It is emphasized first that the magnetosphere is not globally equipotential even in the frame rotating with a central star (i.e. ?#0, where ? is the ‘non-Backus’ potential) due at least to the inertial effects of plasma particles. However, it is shown that the condition ?=0 is asymptotically recovered in the corotating region owing to the presence of the drift current which can be taken into account only when δ is not entirely neglected. This fact suggests that the deviation of the plasma motion in the outer magnetosphere from the corotation can be attributed to the non-zero ?. A globally self-consistent solution is obtained under this condition (?=0). In contrast with the solutions in the ‘force-free’ and the ‘mass-less-electron’ approximations, this solution has a disk structure in the corotation zone in which the plasma and the current density are concentrated to a thin disk near the magnetic equator. Owing to this sheet current in the disk the lines of force of the stellar magnetic field are modified to form a very elongated shape (the magnetodisk) if the plasma β-value is fairly large. Such a disk structure seems to be a common feature in the high β inner magnetospheres of various types of stars. 相似文献
12.
JohannesRuoff Kostas D.Kokkotas 《Monthly notices of the Royal Astronomical Society》2002,330(4):1027-1033
We consider both mode calculations and time-evolutions of axial r modes for relativistic uniformly rotating non-barotropic neutron stars, using the slow-rotation formalism, in which rotational corrections are considered up to linear order in the angular velocity Ω. We study various stellar models, such as uniform density models, polytropic models with different polytropic indices n , and some models based on realistic equations of state. For weakly relativistic uniform density models and polytropes with small values of n , we can recover the growth times predicted from Newtonian theory when standard multipole formulae for the gravitational radiation are used. However, for more compact models, we find that relativistic linear perturbation theory predicts a weakening of the instability compared to the Newtonian results. When turning to polytropic equations of state, we find that for certain ranges of the polytropic index n , the r mode disappears, and instead of a growth, the time-evolutions show a rapid decay of the amplitude. This is clearly at variance with the Newtonian predictions. It is, however, fully consistent with our previous results obtained in the low-frequency approximation. 相似文献
13.
《New Astronomy Reviews》2002,46(8-10):503-506
Broad-band models of the bright NW limb of G347.3–0.5 give convincing evidence that the forward shock of this supernova remnant is accelerating cosmic rays efficiently, placing >25% of the shock kinetic energy flux into relativistic ions. Despite this high efficiency, the maximum electron and proton energies are well below the observed ‘knee’ at ∼1015 eV in the Galactic cosmic-ray spectrum. 相似文献
14.
N. Chamel 《Monthly notices of the Royal Astronomical Society》2008,388(2):737-752
Both relativistic and non-relativistic two-fluid models of neutron star cores are constructed, using the constrained variational formalism developed by Brandon Carter and co-workers. We consider a mixture of superfluid neutrons and superconducting protons at zero temperature, taking into account mutual entrainment effects. Leptons, which affect the interior composition of the neutron star and contribute to the pressure, are also included. We provide the analytic expression of the Lagrangian density of the system, the so-called master function, from which the dynamical equations can be obtained. All the microscopic parameters of the models are calculated consistently using the non-relativistic nuclear energy density functional theory. For comparison, we have also considered relativistic mean field models. The correspondence between relativistic and non-relativistic hydrodynamical models is discussed in the framework of the recently developed 4D covariant formalism of Newtonian multifluid hydrodynamics. We have shown that entrainment effects can be interpreted in terms of dynamical effective masses that are larger in the relativistic case than in the Newtonian case. With the nuclear models considered in this work, we have found that the neutron relativistic effective mass is even greater than the bare neutron mass in the liquid core of neutron stars. 相似文献
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Hasi Ray 《Astrophysics and Space Science》2003,283(3):415-436
Accurate theoretical data for the transition probabilities are highly demanding in astrophysics and in the study of plasma
in astrophysical objects and fusion devices. Na-like highly stripped ions of iron group, specially NiXVIII is very important
in this respect. A highly improved basis in a relativistic many-body coupled-cluster method (CCM) to include correlation properly
is employed to calculate excitation energies, the electric quadrupole (E2) transition line strengths and transition probabilities
for NiXVIII. The effect of correlation is studied thoroughly. The present improved data for different atomic/ionic properties
are compared with the available theoretical and/or experimental data and they are in agreement. Some E2 transition data are
reported for the first time.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
《New Astronomy Reviews》2000,44(7-9):415-417
We have monitored with the RXTE PCA the variability pattern of the 2–20 keV flux in four PG quasars (QSOs) from the Laor et al. (1994) sample. Six observations of each target at regular intervals of 1 day were performed. The sample comprises objects with extreme values of Balmer line width (and hence soft X-ray steepness) and spans about one order of magnitude in luminosity. The most robust result is that the variability amplitude decreases as energy increases. Several options for a possible ultimate driver of the soft and hard X-ray variability, such as the influx rate of Comptonizing relativistic particles, instabilities in the accretion flow or the number of X-ray ‘active sites’, are consistent with our results. 相似文献
18.
The general perturbations in the elliptic and vectorial elements of a satellite as caused by the tidal deformations of the non-spherical Earth are developed into trigonometric series in the standard ecliptical arguments of Hill-Brown lunar theory and in the equatorinal elements ω and Ω of the satellite. The integration of the differential equations for variation of elements of the satellite in this theory is easy because all arguments are linear or nearly linear in time. The trigonometrical expansion permits a judgment about the relative significance of the amplitudes and periods of different tidal ‘waves’ over a long period of time. Graphs are presented of the tidal perturbations in the elliptic elements of the BE-C satellite which illustrate long term periodic behavior. The tidal effects are clearly noticeable in the observations and their comparison with the theory permits improvement of the ‘global’ Love numbers for the Earth. 相似文献
19.
Occurrences of the flare-associated microwave bursts as well as their peak flux and energy excess spectra have been examined in relation to the pre- and post-maximum phases of the respective flares during the period 1969–72. Results obtained are: (i) about 76% of the flare-associated bursts occur in the pre-maximum phase and the remaining 24% occurs in the post-maximum phase irrespective of the flare classification, intensity-wise or area-wise; (ii) ‘impulsive’ and ‘gradual rise and fall’ bursts are relatively more important in the pre-maximum phase while ‘post burst increase’ bursts show comparatively higher occurrences in the post-maximum phase; (iii) peak flux and energy excess spectra of the concurrent microwave bursts in the pre-maximum phase of the flare are mostly of ‘inverted U’ and ‘increasing with frequency’ spectral types. Of these, ‘impulsive’ bursts are predominantly of the ‘inverted U’ and the ‘grf’ bursts are of the ‘increasing with frequency’ spectral type. 相似文献
20.
Yu. I. Morozov 《Astrophysics and Space Science》1987,133(1):107-148
This paper deals with the representation of relativistic equations of gas dynamics with due regard to the general relativity theory effects in the form accepted and widely applied in the special relativity theory. With this purpose, a strict formal definition of a non-inertial co-moving reference frame without rotation is carried out on the basis of a tetrad formalism by use of the Fermi—Walker rules of transport of 4-frame. The equations of physical kinetics, relativistic collapse, Einstein's equations, equations of relatiivistic radiation gas dynamics for ideal and dissipative gases, Taub's equations for a shock wave, which allow for radiation and electron-positron pairs, are obtained in this reference frame. On the basis of the local Lorentz transformation and the Ricci rotation coefficients, these equations are written in the laboratory reference frame, in order to illustrate the fact that the general relativity effects can be simply taken into account in the equations having a form accepted in the special relativity theory. 相似文献