Исследование устойгивости периодигеских движений в окрестности коллинеарных точек либрации

1937 - (, 1938). , , , , . , . . (, 1938), , . - (, 1938; Szebehely, 1967)., , . . - (, 1938), . — — . , , . , . . , . , , . . (, 1944). , .

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In 1937, the Celestial Mechanics and Cosmogony section of the Sternberg State Astronomical Institute undertook the task of evaluating the Gylden-Moulton hypothesis on the origin of the Gegenshein from the standpoint of celestial mechanics. That investigation, which the authors themselves considered preliminary, contains nonetheless a series of important results. For example, G. N. Duboshin showed that in the planar, circular, restricted three-body problem, periodic motion of finite amplitude in the neighborhood of a collinear libration point is unstable according to Lyapunov's criterion both in the proper and in the orbital sense. The latter result is incompatible with the above named hypothesis, and thus appears as one of the serious objections among the many known negative conclusions relative to the existence of the Gylden-Moulton cluster.Unfortunately, most of the specific problems which arose in the above named research have not been considered since. One of these, the problem of the stability of three-dimensional periodic orbits in the neighborhood of a collinear libration point is solved in the present paper, within the limits of the three-dimensional, circular, restricted, three-body problem. Major attention is given to the investigation of stability in the orbital sense, since in the proper sense all orbits are unstable according to Lyapunov theory. It is shown that in order to resolve the question of stability, it is sufficient to consider the equations in their variational form. Analysis of the roots of the corresponding characteristic equations determines the orbital stability of planar and three-dimensional solutions, which later can be confirmed by calculation of the characteristic exponents appearing in the periodic solutions of the N. A. Artemiev method. Finally, the possibility of conditional stability in the linear approximation is proved.

     

Околозвездные оБлака по данным 2800 Mgii

2800 Mgii (. 1). (N ⁺/N ₁1000) , , (N ⁺/N ₁10). , . —, , . — . : ; 0.002 1 , 0.1 ; () 100 ^–3; ; ; , 10 ; 10^–4 1 . 2800 Mgii .     

Структура и эволюция Сверхмассивных вращающихся магнитных политроп

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The structure of rotating magnetic polytropes is considered in Roche approximation. Investigation of the influence of poloidal as well as toroidal magnetic fields on the conditions of the beginning of matter outflow due to rotational instability is carried out. The influence of the turbulent convection and twisting of magnetic force-lines on the time of smoothing of differential rotation is considered. The estimate of the magneto-turbulence energy generated by differential rotation is presented. Both maximum possible energy output and duration of the quasi-statical evolution phase up to the appearance of hydrodynamic instability due to the effects of general relativity are calculated for supermassive magnetic polytropes of index three with uniform or differential rotation. The radius-mass relation is obtained for supermassive differentially-rotating magnetic polytropes referring to the longest part of the quasi-statistical evolution stage; some consequences are pointed out, including the period-luminosity relation.The evolution of the considered models of supermassive rotating magnetic polytropes with different character of rotation and different geometry of a magnetic field is discussed.The results obtained are summarized in the last section.

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English translation will appear in the next issue ofAstrophys. Space Sci.

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Receipt delayed by postal strike in Great Britain     

A Molecular Ring in the Liner Ngc 5218

High resolution OVRO CO 1–0 observations of the inner 30 in the LINER galaxy NGC 5218 reveal the presence of a double centrally peaked molecular concentration with extensions out to a radius of 12. The molecular mass detected is 2.4 × 10⁹ M and the gas surface density is high, 3000 M pc square in the inner 500 pc. The SFR is 2–3 M yr^–1 and the SFE is 13, which are low or moderate values for that gas surface density. We interpret the inner feature as a rotating molecular ring with a radius of 200 pc. We furthermore suggest that the LINER activity in NGC 5218 is not caused by an aging starburst, but by a buried AGN.     

On quasi-integrable problems. The example of the artificial satellites perturbed by the Earth's zonal harmonics

With the Hamiltonian parameters developed for the two-fixed-centers problem a simple and very accurate expression of the quasi-integral can be given for the motion of artificial satellites perturbed by the Earth's zonal harmonics. This motion can be considered as integrable.A theoretical analysis shows that Hénon's semi-ergodic regions or chaotic regions are extremely small in this problem, and almost all orbits are of the regular or quasi-periodic type. Furthermore, the relative difference between the true motion and the corresponding integrable motion remains forever less than 10^–14 for all regular orbits even in the vicinity of critical inclinations.For chaotic orbits this very small difference remains verified at least for centuries, nevertheless there are some exceptional orbits that finally diverge from the integrable model.     

Periodic orbits of stars in axisymmetrical stellar systems

Periodic orbits of stars in axisymmetrical nearly spherical stellar systems have been investigated. Generating orbits have been found among periodic ones relating to the spherically-symmetrical field. The linear approximation appears to be insufficient for constructing periodic trajectories. Possible variants of the generating periodic solutions have been found, which give rise to disturbed periodic orbits in the second approximation.

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Угловые Флуктуации Реликтового излучения, порождаемые космологической турбу лентностью

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On Low-Mass, Strange Quark Stars with a Crust

Low-mass strange stars with a crust are investigated within the framework of the bag model. The crust, which consists of degenerate electrons and atomic nuclei, has a limiting boundary density _cr , which is determined by the mass of the crust, and it cannot exceed the value _drip = 4.3·10¹¹ g/cm³, corresponding to the density at which neutrons drip from nuclei. For different values of _cr in the low-mass range (M 0.1 M) we calculate several series of configurations: we find the dependence of the stellar mass M on the central density _c for _cr = const, with 10⁹ g/cm³ _{cr drip} , and for each series we determine the parameters of the configuration for which the condition dM/d _c > 0 is violated. When the boundary density of the crust decreases to 10⁹ g/cm³, the minimum mass of a strange star decreases to M _min 10^-3 M, while the radius reaches 600 km.     

B,V surface photometry of the UV continuum galaxy NGC 838

Surface photometry of the UV continuum galaxy NGC 838 has been carried out in theB, V system using photographic plates obtained with the 74 Kottamia telescope, Egypt. Isophotes, luminosity profiles, integrated photographic magnitudes, effective diameters and other photometric parameters are derived.The photoelectrically calibrated total apparent magnitudes areB _T =13.57 with maximum diameters 1.57×1.34 (at threshold _m =27.7 mag.//) andV _T =12.91 with maximum diameters 1.54×1.32 (at threshold _m =27.7 mag./). The integrated colour index(B–V) _T =0.66 and the effective surface brightness _e (B=19.0 mag./) and _e (V=19.7 mag./. The major axis is at position angle =85°±1°.The nucleus of NGC 838 is quite blue (integrated colour(B–V)=0.41 forr ^*<0.1) compared to normal galaxies while the colour becomes redder from the nucleus outwards. The UV excess, H emission and radio continuum emission previously observed from this galaxy by other investigators may be attributed to a recent burst of star formation in the nucleus of the galaxy of duration slightly greater than 2×10⁷ yr.     

Комптоновское рассеяние в источниках с синхротронной реабсорбцией

, ( ). n =3–5, T _e =4T _b (1 + ), - ( ) ,T _b - . , . , . W _H , ,n =3, =1. n =3–5(E), (E) , , = 1 – (), |()| < 1, |(E)| < 1. 3 273.     

Волна охлаждения в оьолочках сверхновых звëзд

, . , , . II (m ₀20M ). ( II ) .     

О наблю дениях вспышек звезд в инфракрасных лучах

(Kilyachkoet al., 1978) , . l ( I II). (Kilyachkoet al., 1978) : (1) 800 Å , , UV Cet. EV Lac; (2) UV Cet EV Lac 8000 Å , ; (3) 8000 Å . — MO-KS; (4) 1–3 m.     

Secular perturbations in general planetary theory

Based on a general planetary theory, the secular perturbations in the motion of the eight major planets (excluding Pluto) have been derived in polynomial form. The results are presented in the tables. The linear terms of second order with respect to the planetary masses and the nonlinear terms of first order up to the fifth (and partly seventh) degree with respect to eccentricities and inclinations were taken into account in the right-hand members of the secular system. Calculations were carried out by computer with the use of a system that performed analytic operations on power series with complex coefficients.

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Optical Identification of IRAS Point Sources. Galaxies. X

The tenth list of objects from the BIG (Byurakan-IRAS Galaxies) sample, containing 104 galaxies identified with 60 point sources from the IRAS PSC catalog, is introduced. The identifications have been made in the region +69°+73° and 09^h50^m15^h20^m with an area of 107 sq.deg. The identified objects include 13 Sy candidates, 5 compact star-formation galaxies, 11 interacting pairs (including 5 merger candidates) and 1 interacting triple system, 5 LSB galaxies, and 5 groups. 21 objects are also identified with radio sources. The optical coordinates, their deviations from the IR coordinates, V stellar magnitudes, morphological types, angular sizes of the central regions, and position angles have been determined. The identified galaxies are of Sa-Sc, SB, and Irr morphological types, the optical stellar magnitudes lie in the range 15^m.0-21^m.5, and the angular sizes of the central regions lie in the range 3-32. Finding charts from the DSS2 are included for these objects.     

Равновесие, устойчивость и эволюия вращающегося замагниченного газового диска

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The exact solutions for the equilibrium of rotating gaseous disk with poloidal magnetic field are obtained. The stability of the disk with respect to uniform expansion and contraction is investigated by means of the variational principle. It is shown that if the equilibrium is determined by gravitational and magnetic forces only, the disk is in neutral equilibrium with respect to perturbations of the form r=r. The instability to short-waves perturbations is studied by the quasi-classical method. The analysis shows that if the magnetic field isH>2G, where is the surface density, then these perturbations are stabilized. The configurations of the electrical field induced by the rotation of magnetized disk are found. In conclusion, the questions of the evolution of the disk are discussed in connection with the quasar model when pulsar-like radiation is taken into account.

     

Спектр и поляризация источника синхротронного излучения при релятивистском разлете его компонент

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Пульсар в краБе: замагниченные трещины в коре как ключ к механизмам истечения вещества, радио- и высокочастотного излучений

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Two-body problem with slowly decreasing mass

Summary Evolution of the orbital elements of a two-body system with slowly decreasing mass according to Jeans' mode is described by a non-linear, non-autonomous system of differential equations.In general the system contains one stationary solution (e=1,f=), for which an instability criterion is derived. For example the stationary solution is unstable for all Jeans-Eddington functionsm _n (t) with 1n3 which characterize the loss of mass. Furthermore, it is possible to describe the quantitative behaviour ofE+,e anda for arbitrarym(t) in a large number of cases. In the case of the Jeans-Eddington functions we find that the amplitude of the oscillations ine is monotone decreasing with time ifn>3 and it is monotone increasing with time ifn<3.By comparing these analytical results with the numerical calculations of Hadjidemetriou we explain the rapid rotation of the line of apsides which occurs if the initial value ofe is nearly-circular.

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, , . (e=1,f=), . , -m _n (t), , 1n3. , E+,e a m(t) . - , , n>3, , n<3. , , - e.

     

Horizontal-branch star models

Evolutionary tracks of 0.9M , 0.7M and 0.6M models for Population II stars have been computed in the post-red giant phase. The stars are initially composed of a helium core containing a mass fraction equal to 0.9 and of a hydrogen-rich envelope. They represent hypothetical remnants of stars after substantial mass loss in previous evolutionary phases or/and at the helium flash.u 0,9M , 0,7M 0,6M . , 90% , . , .Riassunto È stata calcolata per modelli di stelle di 0,9M , 0,7M e 0,6M di Popolazione II l'evoluzione successiva allo stadio di gigante rossa. Inizialmente i modelli constano di un nucleo di elio contenente il 90% della massa totale e di un inviluppo idrogenico. Essi possono interpretarsi come i resti di stelle che abbiano perso una frazione di massa considerevole in fasi evolutive precedenti, o all'innesco violento dell'elio al centro.     

Ускорение релятивистских электронов в плазменных реакторах и нелинейные спектры космических радиоисточников

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