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1.
A. A. V’uga 《Astrophysics》2000,43(1):102-106
The random quantity ξ, the number of pairwise mergings for a two-component sample N = N1 + N2, N2≤ N1, is found under the assumption that mergings only between particles of different types are possible. Let T0,T1,T2,..., Tm, ... be a sequence of times. We then have a discrete approximation of the process of mergings by a uniform Markov chain.
Translated from Astrofizika, Vol. 43, No. 1, pp. 137-142, January–March, 2000. 相似文献
2.
In part I we suggested an approximate equation to determine the contribution of relativistic effects to the moment of inertia
of a superdense star. In the present paper it is tested on model neutron stars with nine different variants of the equation
of state of superdense matter. It is established that the approximation error does not exceed 5% for stable configurations.
A more accurate version of the Ravenhall—Pethick equation [D. G. Ravenhall and C. J. Pethick, Astrophys. J., 424, 846 (1994)]
for the moment of inertia as a function of the mass and radius of a neutron star is derived.
Translated from Astrofizika, Vol. 40, No. 4, pp. 507–516, October–December, 1997. 相似文献
3.
In this first part of the work we develop the equations of motion of a triaxial space station in orbit around the oblate Earth. A first order solution of the problem is presented and the method of complete integration of the system is outlined up to second order of approximation. The zero order part of the Hamiltonian includes both the kinetic and potential energy (Earth's Newtonian attraction) of the station, while the motion in the vicinity of a specific configuration is assumed.The solution leads to deviations on the attitude introduced by the oblateness of the Earth. Such attitude is an exact solution of the equations of the station when its center of mass moves in an elliptic Keplerian orbit.The explicit expressions of the complete solution, discussion of other possible effects on the motion and numerical comparisons will be presented in the second part of the work. 相似文献
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Hervé Martin Francis Albarède Philippe Claeys Muriel Gargaud Bernard Marty Alessandro Morbidelli Daniele L. Pinti 《Earth, Moon, and Planets》2006,98(1-4):97-151
Except the old Jack Hills zircon crystals, it does not exit direct record of the first 500 Ma of the Earth history. Consequently, the succession of events that took place during this period is only indirectly known through geochemistry, comparison with other telluric planets, and numerical modelling. Just after planetary accretion several episodes were necessary in order to make life apparition and development possible and to make the Earth surface habitable. Among these stages are: the core differentiation, the formation of a magma ocean, the apparition of the first atmosphere, oceans and continents as well as the development of magnetic field and of plate tectonics. In the same time, Earth has been subject to extraterrestrial events such as the Late Heavy Bombardment (LHB) between 3.95 and 3.8 Ga. Since 4.4–4.3 Ga, the conditions for pre-biotic chemistry and appearance of life were already met (liquid water, continental crust, no strong meteoritic bombardment, etc...). This does not mean that life existed as early, but this demonstrates that all necessary conditions assumed for life development were already present on Earth. 相似文献
6.
D. I. Nagirner 《Astrophysics》1994,37(4):362-371
The method of computing the radiation field in an infinite circular cylinder proposed in Part I is now applied to the case of isotropic scattering with sources on the boundary and axis of the cylinder, as well as for a uniform distribution of sources inside the cylinder. For the simplest kernel we obtain exact solutions of the basic integral equation in explicit form. For scattering in a spectral line with complete frequency redistribution and a power absorption profile we develop an asymptotic theory for the case when the optical radius of the cylinder is large. We solve the asymptotic equations for the basic characteristics of the scattering in closed form for conservative scattering and find its asymptotics. We obtain estimates of the mean number of scatterings with a layered source, and also the mean and variance of the number of scatterings with a uniform source distribution.Translated fromAstrofizika, Vol. 37, No. 4, 1994.This work was carried out with the financial support of the Russian Basic Research Fund (grant 93-02-2957). 相似文献
7.
An extensive set of realistic equations of state for superdense matter with a quark phase transition is derived on the basis of the three equations of state for neutron matter and the eight variants of strange quark-gluon plasmas in the MIT quark bag model. The characteristics of the phase transitions are described and the calculated equations of state with a density jump are studied in detail. 相似文献
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9.
G.D. Parker 《Planetary and Space Science》1982,30(1):57-66
Power spectra of vector components of interplanetary magnetic field fluctuations near 4–5 a.u. during quiet intervals show a frequency dependence very close to fs over the frequency range 4 × 10?5 to 9 × 10?3 Hz (corresponding to periods of 7 h-2 min). While the spectra are generally very close to power law in frequency, variations in slope among the spectra exceed those expected from random errors and may represent true temporal variations. Mean slopes corrected for systematic error are s = ? 1.50±0.02 (Pioneer 10, mean heliocentric distance 5.3 a.u.) and s = ? 1.52±0.02 (Pioneer 11, mean heliocentric distance 3.9 a.u.) and are consistent with several determinations of spectral slope for magnetic fluctuations near 1 a.u. Radial evolution of the perturbations is investigated by choosing data samples in which Pioneer 10 and 11 and the sun are nearly colinear. The dependence on heliocentric distance of σc2, the composite vector variance, and of σc/Bmag, where Bmag is the mean magnitude of the magnetic field, show that the radial variation of fluctuation amplitude is highly variable in time with a dependence on heliocentric distance typically in the range R?1 to R?1.5. These observations are compared with theoretical models of outward propagating Alfven waves of solar origin and of MHD turbulence. The mean slopes agree well with that expected for turbulence. The significant variability observed in spectral slopes and in the radial dependence of fluctuation amplitude in data selected specifically for conditions of relative magnetic quiet is noteworthy and urges caution in modeling heliospheric magnetic microstructure in studies of galactic cosmic ray modulation. 相似文献
10.
This is an examination of the gravitational instability of the major large-scale perturbation modes for a fixed value of the
azimuthal wave number m = 1 in nonlinearly nonstationary disk models with isotropic and anisotropic velocity diagrams for
the purpose of explaining the displacement of the nucleus away from the geometric center (lopsidedness) in spiral galaxies.
Nonstationary analogs of the dispersion relations for these perturbation modes are obtained. Critical diagrams of the initial
virial ratio are constructed from the rotation parameters for the models in each case. A comparative analysis is made of the
instability growth rates for the major horizontal perturbation modes in terms of two models, and it is found that, on the
average, the instability growth rate for the m = 1 mode with a radial wave number N = 3 almost always has a clear advantage
relative to the other modes. An analysis of these results shows that if the initial total kinetic energy in an isotropic model
is no more than 12.4% of the initial potential energy, then, regardless of the value of the rotation parameter Ω, an instability
of the radial motions always occurs and causes the nucleus to shift away from the geometrical center. This instability is
aperiodic when Ω = 0 and is oscillatory when Ω ≠ 0 . For the anisotropic model, this kind of structure involving the nucleus
develops when the initial total kinetic energy in the model is no more than 30.6% of the initial potential energy. 相似文献
11.
The products from spark and semi-corona discharges through mixtures simulating the Jovian atmosphere were analyzed by gas chromatography combined with mass spectrometry. When the reaction was performed at ?80°C, 3-ethylaminopropionitrile and a number of higher homologs were formed. On the other hand, at +20°C, higher molecular-weight material appeared which yielded aminonitrile- derived fragments on mass spectrometry. Although the spectra were not identical, there were notable similarities between these and the mass spectra of some compounds present in the Murray and Orgeuil meteorites. Aminonitriles may occur as minor constituents of the Jovian atmosphere and perhaps by cyclization may produce pyrimidines. 相似文献
12.
A.A. V’uga 《Astrophysics》1999,42(4):460-466
A random quantity ξ, the number of pairwise mergings in a finite set of particles, is constructed in a sequential scheme of
complex trials. Let T0, T1,T2,…, Tm,…be a sequence of times. We then have a discrete approximation of the process of mergings
by a uniform Markov chain.
Translated from Astrofizika, Vol. 42, No. 4, pp. 609–616, October–December, 1999. 相似文献
13.
D. I. Nagirner 《Astrophysics》1995,38(1):39-47
We present a method for computing the spectrum of the integral equation for radiation transfer in a cylinder. This method, as in the previous articles in this series, is based on a Hankel transformation applied to the equation. Calculating the spectrum then reduces to solving the equation for the auxiliary function for each eigenvalue separately. The corresponding eigenfunction is then found by an additional integration. We find asymptotic expressions for the eigenvalues and the eigenfunctions for a cylinder with a large optical radius when there is scattering in a spectral line, with complete redistribution over frequency when the absorption coefficient obeys a power law. We also derive equations determining the quantities entering into these expressions. For the simplest kernel of the equation all quantities can be expressed in terms of Bessel functions and roots of a transcendental equation.Translated from Astrofizika, Vol. 38, No. 1, pp. 75–88, January–March, 1995. 相似文献
14.
The stationary two-dimensional magnetohydrodynamic solution for the accretion of the matter without pressure into a gravitating centre of a black hole is obtained. It is assumed that the magnetic field far from the collapsed star is homogeneous and its influence on the flow is negligible. Around the star, at the plane perpendicular to the direction of the magnetic field, the dense quasistationary disc is formed, the structure of which in a large extent is determined by dissipation processes. The structure is calculated for (a) a laminar disc with the Coulomb mechanism of dissipation; and (b) a turbulent disc.The estimations of the parameters of the shock which result from the infall of the matter onto the disc are given. In the last section the numerical estimation and approximate character of the radiation spectrum of the disc and the shock are obtained for two cases of 10M
and 105
M
. The luminosity of collapsed objects withM=10M
appears to be about solar, thus its observation is possibly only at the distances less than 300–1000 pc. The collapsed objects in the Galaxy withM=105
M
could constitute very bright sources in spectral regions from optical up to X-ray. The spectra of a laminar and a turbulent disc for 10M
black hole are very different. The laminar disc radiates primarily in the ultraviolet. The turbulent disc radiates a large part of its flux in the infrared. Therefore, one cannot exclude the possibility that some of the galactic infrared star-like sources are individual black holes in the accretion state. 相似文献
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B. P. Kondrat'ev 《Astrophysics》1989,31(2):632-644
Pedagogical Institute, Glazov. Translated from Astrofizika, Vol. 31, No. 2, pp. 369–387, September–October, 1989. 相似文献
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B. P. Kondratyev 《Solar System Research》2012,46(5):352-362
A fundamentally new approach to an elliptic Gaussian ring has been developed. It has been ascertained that it can be produced from a uniform plane elliptic disk by mass balayage into an elementary homothetic layer with the center of homothety at an ellipse focus. An advantage of new interpretation is in the fact that the spatial potential of a Gaussian ring is expressed in terms of the potential of a uniform elliptic disk, well-known in the finite form, and its derivatives. A general formula for the potential of a two-dimensional homothetic layer has been derived with this purpose. As a result, the potential of a Gaussian ring is represent-able in a simple analytical form in terms of standard complete elliptic integrals in both elliptic and Cartesian coordinates. The mass asymmetry along the ring is considered explicitly. The potential formulas are verified numerically and have no singular points at ellipse foci. Particular cases are considered; the 3D potential surface and system of equipotentials are constructed. Knowledge of the potential extends the range of application of a Gaussian ring in the problem of calculation of secular perturbations in celestial mechanics. 相似文献
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