共查询到20条相似文献，搜索用时 15 毫秒
1.
Emmanuel Davoust 《Celestial Mechanics and Dynamical Astronomy》1983,31(3):303-315
We use the analytical method of Lindstedt to make an inventory of the families of periodic orbits in a two-dimensional galactic potential first introduced by Contopoulos (1960). We examine the general case of orbital resonance and its neighborhood; two special cases, the 1∶1 and 2∶1 resonances are dealt with separately. The present paper provides a synthesis and an extension of earlier works on this potential in the neighborhood of the integrable case (ε?1). 相似文献
2.
P. Magnenat 《Celestial Mechanics and Dynamical Astronomy》1982,28(3):319-343
The locations and stability features of the main symmetrical periodic orbits in the potential $$V = \tfrac{1}{2}\left( {Ax^2 + By^2 + Cz^2 } \right) - \varepsilon xz^2 - \eta yz^2 with \sqrt {A:} \sqrt {B:} \sqrt C = 6:4:3$$ are calculated. Two resonant 1-periodic orbits reveal themselves to be the most important of the system. The third dimension and the additional coupling term have a large effect upon the emergence and stability of p.o. prolongated from the bi-dimensional cases 4∶3 and 2∶1. The existence of three main instability types leads to behaviours much more complicated than in systems with two degrees of freedom. Particularly the presence of complex instability, a new feature with respect to bi-dimensional problems, may produce large instability regions in the set of initial conditions. Some asymptotic curves emanating from unstable orbits are calculated in the four-dimensional space of section. The aspect of such curves is considerably modified when a perturbation is added in the third dimension. The neighbourhood of orbits suffering from complex instability is studied in the space of section and by means of the maximum Lyapunov Characteristic Number technique. It is shown that the motion can deviate far from the vicinity of the p.o. representative point as soon as the orbit is of complex instability. When the perturbation is large enough, the stochasticity produced by this type of instability can be very important. 相似文献
3.
A review is given of observations and theories relevant to the solar flare of 21 May, 1980, 20 ∶ 50 UT, the best studied flare on record. For more than 30 hr before the flare there was filament activation and plasma heating to above 10 MK. A flare precursor was present ≥6 min before the flare onset. The flare started with filament activation (20 ∶ 50 UT), followed by thick-target heating of two footpoints and subsequent ablation and convective evaporation involving energies of 1 to 2 × 1031 erg. Coronal explosions occurred at 20 ∶ 57 UT (possibly associated with a type-II burst) and at 21 ∶ 04 UT (associated with an Hα spray?). Post-flare loops were first seen at 20 ∶ 57 UT, and their upward motion is interpreted as a manifestation of successive field-line reconnections. A type-IV radio burst which later changed into a type-I noise storm was related to a giant coronal arch located just below the radio noise storm region. Some implications and difficulties these observations present to current flare theories are mentioned. 相似文献
4.
E. W. Cliver S. W. Kahler H. V. Cane M. J. Koomen D. J. Michels R. A. Howard N. R. Sheeley Jr. 《Solar physics》1983,89(1):181-193
We use a variety of ground-based and satellite measurements to identify the source of the ground level event (GLE) beginning near 06∶30 UT on 21 August, 1979 as the 2B flare with maximum at ～06∶15 UT in McMath region 16218. This flare differed from previous GLE-associated flares in that it lacked a prominent impulsive phase, having a peak ～9 GHz burst flux density of only 27 sfu and a ?20 keV peak hard X-ray flux of ?3 × 10-6 ergs cm-2s-1. Also, McMath 16218 was magnetically less complex than the active regions in which previous cosmic-ray flares have occurred, containing essentially only a single sunspot with a rudimentary penumbra. The flare was associated with a high speed (?700 km s-1) mass ejection observed by the NRL white light coronagraph aboard P78-1 and a shock accelerated (SA) event observed by the low frequency radio astronomy experiment on ISEE-3. 相似文献
5.
We study the connection between radial systems of dark globules and stellar associations. It is shown that of the 17 systems of type 1 in Table 1 of [1] 16 radial systems are connected with known associations. A new association is found (missing from the catalogs) connected with the remaining system (System No. 2). Four systems of the six systems of type 2 (Table 2 of [1]) are connected with known associations. A new method of determining the distance to associations is proposed, using the mean linear thickness of dark globules of radial systems connected with these associations as the criterion for distance. Using this method we make the distance to the association Cyg OB 9 more precise and answer the question whether several radial systems belong to the corresponding stellar associations.Translated fromAstrofizika, Vol. 37, No. 4, 1994.The authors are grateful to Academician V. A. Ambartsumyan for constant attention to this work. 相似文献
6.
本文讨论了摄谱仪中若干畸象系统,它们的作用是缩放入射狭缝的象单在高或宽的方向的尺寸,这等效于在狭缝前、后单在子午面内或弧矢面(色散方向面)内改变光束的孔径角,也等效于准直光束单在子午面或弧矢面内缩放光束宽度,在讨论中指出了准直畸象系统优于非准直畸象系统。 在着重讨论和分析准直畸象系统的不同形式时,我们提出了棱镜系统,它具有许多优点,是最为可行的方案。 相似文献
7.
We present in this paper the evolutionary characteristics of the systems belonging to two evolution types, designated as 1C2COf and 1Nc2COf, among seven evolution types which were studied in the preceding paper of this series. These two types are most complicated and interesting in the evolutionary behaviour, which consists of repeated detached, semi-detached, and contact phases. We discuss observational aspects of the results. Evolutionary behaviour of the systems are also discussed, compared with the thermal relaxation oscillation model. 相似文献
8.
Cui Zhen-Xing 《Chinese Astronomy and Astrophysics》1987,11(4):291-296
The method of identifying absorption line systems in QSO spectra (Cui et al. 1983; Chen et al. 1983) is further developed here. Certain limitations of the method and their improvements are discussed. Certain other problems requiring further study are pointed out. The improved method is applied to PKS 0528-250, and gives two new absorption line systems Za = 0.065 and 0.0345 in addition to the four systems Za = 2.8110, 2.8130, 2.5275, 2.1410, consistent with the systems A1A2, B, C of Norton et al. (1980). However, the systems D1, D2, E, F and G of Chen and Norton (1984) are not recovered. The reason for this discrepancy is discussed. 相似文献
9.
Using a consistent perturbation theory for collisionless disk-like and spherical star clusters, we construct a theory of slow
modes for systems having an extended central region with a nearly harmonic potential due to the presence of a fairly homogeneous
(on the scales of the stellar system) heavy, dynamically passive halo. In such systems, the stellar orbits are slowly precessing,
centrally symmetric ellipses (2: 1 orbits). We consider star clusters with monoenergetic distribution functions that monotonically
increase with angular momentum in the entire range of angular momenta (from purely radial orbits to circular ones) or have
a growing region only at low angular momenta. In these cases, there are orbits with a retrograde precession, i.e., in a direction
opposite to the orbital rotation of the star. The presence of a gravitational loss-cone instability, which is also observed
in systems of 1: 1 orbits in near-Keplerian potentials, is associated with such orbits. In contrast to 1: 1 systems, the loss-cone
instability takes place even for distribution functions monotonically increasing with angular momentum, including those for
systems with circular orbits. The regions of phase space with retrograde orbits do not disappear when the distribution function
is smeared in energy. We investigate the influence of a weak inhomogeneity of a heavy halo with a density that decreases with
distance from the center. 相似文献
10.
Higher order corrections (up to n-th order) are obtained for the perihelion precession in binary systems like OJ287 using the Schwarzschild metric and complex integration. The corrections are performed considering the third root of the motion equation and developing the expansion in terms of \(r_{s}/ (a(1-e^{2}) )\).The results are compared with other expansions that appear in the literature giving corrections to second and third order. Finally, we simulate the shape of relativistic orbits for binary systems with different masses. 相似文献
11.
X-ray binaries such as Cen X-3, Cyg X-1, Vela X-1, 2U1700-37, SMC X-1, Cir X-1, with periods ranging from 2d.087 to 12d.28, are probably evolution products of massive binary systems. The massive primary starts losing mass after core hydrogen burning and undergoes a supernova explosion. The evolution of binary systems consisting of a 20M⊙ primary and secondaries of respectively 14, 10, 8 and 6M⊙ was computed from Main Sequence stage through the X-ray phase, until the second mass transfer phase. Estimates were performed for the evolution of a secondary of 4M⊙. It may be seen that some of these systems during their X-ray phase match the observed mass ratios and periods. 相似文献
12.
Detailed mapping in a 14,000,000 km2 area of northwestern Guinevere Planitia and northern Beta Regio bounded by 264°-312°E, 24°-60°N has revealed thousands of long extensional lineaments (graben, fissures and related fractures). These can be grouped into radiating, circumferential and linear systems. Thirty four radiating systems have been identified, of which 16 have radii greater than 300 km and eight have radii greater than 1000 km. Twenty six linear (straight) systems with a length greater than 300 km have been distinguished of which six have a length greater than 1000 km. Linear systems are generally associated with rifts, although some may represent distal portions of radiating systems. In addition, 19 circumferential systems, some associated with coronae, have been identified. The distribution of each system is compared with the host geology in order to place the graben-fissure systems in a regional stratigraphic framework. The majority of systems are: (1) younger than tesserae, ridge belts and densely fractured plains, (2) coeval with, and in many cases, define fracture belts, (3) partially flooded by wrinkle-ridged plains units, and (4) older than smooth and lobate plains units and young rifts. The inventory of radiating graben-fissure systems that we catalogue represents a database of tectono-magmatic centers that complements the centers defined using other criteria, e.g., large volcanoes, coronae, and shield fields. We have attempted to identify those systems that are underlain by dike swarms in order to evaluate their relationship to mantle plumes. At least 11 of the radiating systems extend well beyond any central topographic uplift and are therefore interpreted to be underlain by dike swarms. 相似文献
13.
本文采用Wilson-Devinney的Roche模型,对两颗短周期食双星ST Car和RY Ind的光变曲线,进行了再分析。结果表明ST Car的测光质比q=0.60,RY Ind的q=0.50,两颗均属分离的不接双星,但它们的小质量次子星几乎充满Roche临界面。两星的测光特性说明,它们可能是Algol演化阶段后的双星。 相似文献
14.
An analysis of the light curves using the Wilson–Devinney code for NSV 3497 and NSV 13890 is provided. Both systems are found
to be A-Type systems with a mass ratios (q= M2/M1) of 0.22 and 0.0801, respectively. A review of the astrophysical quantities suggests that the systems generally demonstrate
properties typical of other contact systems. 相似文献
15.
We consider the general spatial three body problem and study the dynamics of planetary systems consisting of a star and two planets which evolve into 2/1 mean motion resonance and into inclined orbits. Our study is focused on the periodic orbits of the system given in a suitable rotating frame. The stability of periodic orbits characterize the evolution of any planetary system with initial conditions in their vicinity. Stable periodic orbits are associated with long term regular evolution, while unstable periodic orbits are surrounded by regions of chaotic motion. We compute many families of symmetric periodic orbits by applying two schemes of analytical continuation. In the first scheme, we start from the 2/1 (or 1/2) resonant periodic orbits of the restricted problem and in the second scheme, we start from vertical critical periodic orbits of the general planar problem. Most of the periodic orbits are unstable, but many stable periodic orbits have been, also, found with mutual inclination up to 50?–60?, which may be related with the existence of real planetary systems. 相似文献
16.
崔振兴 《中国天文和天体物理学报》1987,(3)
本文对崔振兴和陈建生等人所提出的类星体吸收线红移系统证认方法作了进一步探讨。指出了方法的局限性及改进的办法;也指出了有待于今后继续研究的问题;并将改进后的方法应用于类星体PKS 0528-250的光谱分析中,得到了它的吸收线红移系统有:Z_a=2.8110,2.8130,2.5375,2.1410。这和Morton等(1980)所得的A_1,A_2,B,C红移系统一致。另外,我们又得到的新系统是Z_a=0.0345,0.0065。Chen和Morton(1984)所得到的D_1,D_2,E,F,G系统,我们未发现。讨论了产生这种差别的原因。 相似文献
17.
T. J. Herczeg 《Astrophysics and Space Science》1988,142(1-2):89-95
Summary Multiplicities recorded in catalogues as well as in the current literature are considered. The basis of the statistical treatment
is about one half of the material collected in theSeventh Catalogue of spectroscopic binaries by A. Batten and his collaborators, subjected also to a magnitude limit atV=6.8, altogether 310 systems. It is hoped that this sample of brighter stars represents close and also wider systems with
a reasonable degree of completeness.
Incidence of higher multiple systems, in particular of ab-c-type triple stars, turns out rather high: the ratio of double
to multiple systems is about 2:1, in terms of the directly observed data. Allowing for some more obvious observational bias,
this ratio approaches 1:1. The number of individual components in multiple systems is almost certainly superior to that of
double star components.
An investigation in progress, concerning multiplicities in the specific classes of W UMa-systems and cataclysmic variables,
is briefly described. 相似文献
18.
We present the aim and first results of the RApid Temporal Survey (RATS) made using the Wide Field Camera on the Isaac Newton Telescope. Our initial survey covers 3 square degrees, reaches a depth of V ∼ 22.5 and is sensitive to variations on time-scales as short as 2 min: this is a new parameter space. Each field was observed for over 2 h in white light, with 12 fields being observed in total. Our initial analysis finds 45 targets which show significant variations. Around half of these systems show quasi-sinusoidal variations: we believe they are contact or short period binaries. We find four systems which show variations on a time-scale less than 1 h. The shortest period system has a period of 374 s. We find two systems which show a total eclipse. Further photometric and spectroscopic observations are required to fully identify the nature of these systems. We outline our future plans and objectives. 相似文献
19.
Method of identifying absorption systems in quasar spectra. II. Application to OQ 172 and discussion
Chen Jian-sheng Cui Zhen-xing Bian Yu-lin Tang Xiao-ying Zou Zhen-long 《Chinese Astronomy and Astrophysics》1983,7(4):280-287
1. According to the principle and procedure given in Ref. [1], we have identified the absorption systems in the spectrum of the high-redshift quasar OQ 172 (PKS 1442 + 101). Four systems were found. Their redshifts are 2.07010, 2.56312, 0.17546 and 0.17910. 2. We have checked the model of random identification in Ref. [1] using Monte Carlo methods [2]. The results were satisfactory. 3. We discuss the advantages of the method of [1] and the problems that await further investigation. It is stressed that the method of [1] avoids certain selection effects that affect the usual methods. 相似文献
20.
The morphological distinction between DP 2 fluctuations and polar substorms (DP 1) is explained, and the relation between these two modes of the disturbance is examined. It is found that although DP 1 and 2 tend to occur together, they are not coherent, indicating that they are driven by different electric field systems. The distinction between DP 2 fluctuations and sudden impulses is also discussed. 相似文献