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1.
我们分析了强γ爆和弱γ爆与不同富性的Abell团之间的交叉相关特性。发现弱γ爆与所有富性的Abell团都没有交叉相关,而强γ爆除了与R≥2的Abell团没有交叉相关外,与R=0,R=1的Abell团都有1σ以上的交叉相关。 相似文献
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本用团分析法分别对距离类D=5及D=6的Abell-ACO团的二维分布进行了分析,分析的目的是探讨星系团分布中可能存在的超大尺度结构,分析结果表明,富星系团分布中的确存在尺度〉100h^-1Mpc的超大尺度结构,本的分析为超大尺度结构的存在提供了又一支持。 相似文献
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本利用在考虑团内星系面数密度分布的前提下,以视向速度为判据,按最大似然原理解算团分布参数和成员概率的严格统计方法,对8个Abell星系团进行了成员研究。解算结果表明此方法是合理的、有效的,星系团的速度弥散度分布与动力学模型一致。有迹象表明椭长形的结构在星系团中是一种普遍现象。从这8个团得到了清晰的NA-σc的相关关系,进而推知团的质光比为100h100^-1 ̄600h100^-1,平均350h1 相似文献
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本假定γ暴来自对论性Beaming其方向满足随机分布,γ暴在自己的静止参考系中满足标准烛光和幂律谱假设,假设暴的发生率密度在Ω=1,A=0的Friedmann宇宙模型下,共动坐标系中是常数,模型对于Beaming的速度非常敏感,当洛仑兹因子Г值小于10幂律谱指数小于1时,计算的统计分布与弱暴的BATSE数据及强暴的PVO数据分布一致。 相似文献
5.
朱杏芬 《中国天文和天体物理学报》1997,(2)
本文采用覆盖全天区的HB类星体表和ACO星系团表为样本,对不同类型的Abel星系团进行分类研究,发现不同类型的星系团与类星体的成协有不同的特性.两样品的KS检验证实与Abel成协(或反成协)的类星体与全部类星体不是出自同一母体,说明这种成协(或反成协)是真实的,不是由投影效应引起的.进一步的计算得到,D4的Abel团对其周围成协类星体的密度增强因子q=1.089,R2的Abel团对其周围的类星体的吸收星等AB=0.09. 相似文献
6.
根据van der Veen(1988)划分的IRAS PSC的IRAS双色图区域选择了一批富氧AGB星的样本,对其银河系分布进行的分析表明:它们属于盘星系,主要分布在旋臂上,将其旋臂结构与已知的HII区的旋臂结构进行拟合,得到这批富氧AGB星的平均光度为8300L⊙(R。=8.0kpc), 相似文献
7.
本文利用Kent和Gunn提供的COMA团天区414个星系的视向速度资料,以及关于团成员的统计判别结果,对COMA团进行了动力学方面的讨论,分析表明COMA团不存在显著动力学效应的整体转动。利用King-Michie模型拟合得到COMA团的核半径为5.'2(相当于210kpc,取H0=50km·s-1·Mpc-1),特征速度弥散度为935km·s-1.从动力学模型的角度来看,COMA团有较为明显的形态分层。有迹象表明团中心区域的次结构是存在的。 相似文献
8.
本利用Kent和Gunn提供的COMA团天区414个星系的视向速度资料,以及关于团成员的统计判别结果,对COMA团进行了动力学方面的讨论。分析表明COMA团不存在显动力学效应的整体转动。利用King-Michie模型拟合得到COMA团的核半径为5。'2(相当于210kpc,取H0=50km·s^-1·Mpc^-1),特征速度弥散度为935km·s^-1。从动力学模型的角度来看,COMA团有较为 相似文献
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Many asteroids with a semimajor axis close to that of Mars have been discovered in the last several years. Potentially some of these could be in 1:1 resonance with Mars, much as are the classic Trojan asteroids with Jupiter, and its lesser-known horseshoe companions with Earth. In the 1990s, two Trojan companions of Mars, 5261 Eureka and 1998 VF31, were discovered, librating about the L5 Lagrange point, 60° behind Mars in its orbit. Although several other potential Mars Trojans have been identified, our orbital calculations show only one other known asteroid, 1999 UJ7, to be a Trojan, associated with the L4 Lagrange point, 60° ahead of Mars in its orbit. We further find that asteroid 36017 (1999 ND43) is a horseshoe librator, alternating with periods of Trojan motion. This asteroid makes repeated close approaches to Earth and has a chaotic orbit whose behavior can be confidently predicted for less than 3000 years. We identify two objects, 2001 HW15 and 2000 TG2, within the resonant region capable of undergoing what we designate “circulation transition”, in which objects can pass between circulation outside the orbit of Mars and circulation inside it, or vice versa. The eccentricity of the orbit of Mars appears to play an important role in circulation transition and in horseshoe motion. Based on the orbits and on spectroscopic data, the Trojan asteroids of Mars may be primordial bodies, while some co-orbital bodies may be in a temporary state of motion. 相似文献
12.
Magnetars are the neutron stars with the highest magnetic fields up to 1015–1016 G. It has been proposed that they are also responsible for a variety of extra-galactic phenomena, ranging from giant flares in nearby galaxies to fast radio bursts. Utilizing a relativistic mean field model and a variable magnetic field configuration, we investigate the effects of strong magnetic fields on the equation of state and anisotropy of pressure of magnetars. It is found that the mass and radius of low-mass magnetars are weakly enhanced under the action of the strong magnetic field, and the anisotropy of pressure can be ignored. Unlike other previous investigations, the magnetic field is unable to violate the mass limit of the neutron stars. 相似文献
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Time scales of the transition from contact binary systems of the W UMa type to single stars of the blue straggler type are estimated. A model of one-way mass transfer from the primary component to the companion inside a common envelope (Eggen et al.) and a model of a contact binary lying on the zero-age main sequence with a companion that is losing mass (F. van't Veer) are used to calculate these scales. The merging times of components were calculated for 304 contact systems of the W UMa type from the Catalog of Approximate Photometric and Absolute Elements of Eclipsing Variable Stars on a scale of loss of mass and orbital angular momentum due to magnetic braking, under the assumption of synchronization of the axial rotation and orbital revolution. On the basis of the resulting statistics, the characteristic merging scales are 0.4-0.6 and 0.5-0.7 Gyr, respectively, for the above two models. The results of a comparison with the work of other authors are discussed. 相似文献
14.
分析了上两个世纪发生在淮河的洪水事件的可公度性,根据其可公度值及其黄金分割点指出1991年与2003年淮河洪水的不可避免,最后讨论了可公度性的局限及淮河洪水可公度值的可能机制。 相似文献
15.
We present a numerical method for inverting long-period components of lightcurves of asynchronous binary asteroids. Data of five near-Earth binary asteroids, (175706) 1996 FG3, (65803) Didymos, (66391) 1999 KW4, (185851) 2000 DP107 and (66063) 1998 RO1, for two of them from more than one apparition, were inverted. Their mutual orbits' poles and Keplerian elements, size ratios, and ellipsoidal shape axial ratios were estimated via this inversion. The pole solutions and size ratios for 1999 KW4 and 2000 DP107 are in a good agreement with independent estimates from radar measurements. We show that uncertainties of estimates of bulk densities of binary systems can be large, especially when observed on short arcs. 相似文献
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Influences of the mass, moment of inertia, rotation, absence of stability in the atmosphere and some other parameters of neutron stars on the evolution of pulsars are examined. It is shown that the locations and evolutions of soft gamma repeaters, anomalous X-ray pulsars and other types of pulsar on the period versus period derivative diagram can be explained adopting values of B < 1014 G for these objects if they have smaller mass (e.g. about 0.5 Solar mass) compared to the conventionally adopted values of mass. This approach gives the possibility to explain many properties of different types of pulsar. 相似文献
18.
Pavel Mayer Marek Wolf P. G. Niarchos K. D. Gazeas V. N. Manimanis Drahomír Chochol 《Astrophysics and Space Science》2006,304(1-4):39-41
New precise times of minimum light for several early-type eclipsing binaries were obtained at three observatories. The changes of period of the following measured binaries are discussed: V1182 Aql, LY Aur, SZ Cam, FZ CMa, QZ Car, LZ Cen, V606 Cen, AH Cep and TU~Mus. 相似文献
19.
This paper deals with the observed variation in the flattening of galaxies with the density of galaxies in the subclusters
of Coma surrounding NGC 4889, NGC 4874, and NGC 4839 based on data from the Abastumani Combined Catalog of Galaxies. The mean
values of the observed ratios of the diameters of the galaxies, as well as histograms of their distributions, indicate that
in the central, dense regions of the subclusters within a volume of 0.5h
75
−1
Mpc3, E and S0 type galaxies are close to spheroidal. A significant reduction in the mean values of the diameters of the galaxies
in the subclusters is noted, regardless of their morphology relative to the galaxies in the halo of the Coma cluster. In the
subclusters, spiral galaxies are found with a hydrogen deficit that is more than 5 times the hydrogen deficit in spirals within
the halo of the cluster. According to their 3-D coordinates, most of the galaxies with a hydrogen deficit are located closer
to the south-east edge of the subcluster surrounding NGC 4874 near an extended gas filament in the x-ray region. This may
indicate that the subcluster is moving toward a central condensation of faint galaxies in the Coma cluster and a possible
merger with it.
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Translated from Astrofizika, Vol. 50, No. 3, pp. 355–368 (August 2007). 相似文献
20.
V.S. Kalantonis E.A. Perdios A.E. Perdiou O. Ragos M.N. Vrahatis 《Astrophysics and Space Science》2003,288(4):479-488
The techniques used for the numerical computation of families of periodic orbits of dynamical systems rely on predictor-corrector
algorithms. These algorithms usually depend on the solution of systems of approximate equations constructed from the periodicity
conditions of these orbits. In this contribution we transform the root finding procedure to an optimization one which is applied
on an objective function based on the exact periodicity conditions. Thus, the determination of periodic solutions and families
of such orbits can be accomplished through unconstrained optimization. In this paper we apply and compare some well-known
minimization methods for the solution of this problem. The obtained results are promising.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献