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1.
本探讨脉冲星ＰＳ４２２１７＋４７分米波段流量变化的星际折射闪烁解释。利用衍射闪烁测量所获得的星际介质参数和连续介质的折射闪烁理论，计算了多频率（０．３１，０．４２，０．６１和０．７５ＧＨｚ）上的折射闪烁结构函数，并与观测结构函数加以比较，结果表明，如果星际介质电子密度不均匀性具有幂律谱，那么幂律指数β＝１１／３（即Ｋｏｌｍｏｇｏｒｏｖ谱）能更好地符合观测。 相似文献
2.
本文分析类星体０９１７＋６２在波长６ｃｍ和１１ｃｍ上快速变化（时标１天）的结构函数．讨论在什么条件下，这种快速变化可用星际折射闪烁来解释．结果表明，折射闪烁解释对星际介质和射电源结构提出了相当明确的限制：散射介质应为连续介质，其有效距离应０．４ｋｐｃ；射电源应包含０．０５—０．１ｍａｓ的致密结构．对快变射电源方向上脉冲星的测量以确定星际介质特性和用ＶＬＢＩ测量快变射电源中的小角径成分，将是检验星际折射闪烁解释的必要途径． 相似文献
3.
本文用比较严格的理论讨论了由连续介质和散射薄屏组成的星际介质对河外射电源的折射闪烁．对折射闪烁引起的流量变化的结构函数Ｄ（τ）（τ为迟后时间）的计算表明，结构函数的幂律部份的指数Ｐ（Ｄ（τ）（∝τＰ）依赖于上述两个成份的相对散射强度，即在连续介质散射为主的情况下；而在薄屏散射为主的情况下；若两个成份的散射可相比较时，１＜Ｐ＜２．因此本模型可以用于解释在河外射电源和脉冲星中观测到的折射闪烁的结构函数具有不同幂指数的情形，特别是Ｐ～１．５的情形． 相似文献
4.
利用星际介质的折射闪烁解释在ＢＬ Ｌａｃ天体０７１６＋７１中观测到的射电快速变化的结构函数，确定了对射电源的结构和散射介质特性所提出的条件，为了解释这个源内观测到的射电变化的“快模式”和“慢模式”的转换，必须考虑射电源内致密结构的角径或运动状态的快速变化，射电变化和光学变化的相 性仍然是折射闪烁解释的难于克服的困难。 相似文献
5.
钱善瑎 《中国天文和天体物理学报》1994,(4)
利用星际介质的折射闪烁理论解释在ＢＬＬａｃ天体０７１６＋７１中观测到的射电快速变化的结构函数，确定了对射电源结构和散射介质特性所提出的条件。为了解释这个源内观测到的射电变化的“快模式”和“慢模式”的转换，必须考虑时电源内致密结构的角径或运动状态的快速变化。射电变化和光学变化的相关性仍然是析射闪烁解释的一个难于克服的困难。 相似文献
6.
综述了脉冲星星际闪烁观测研究的进展，对脉冲星星际闪烁现象，星际介质中电子密度涨落谱，散射等离子体在银河系中的分面等方面的最新研究结果作了介绍。星际闪烁现象和昨际介质的深入理解，使脉冲星星际闪烁已成为研究诸如脉冲星辐射区结构和脉冲星速度等脉冲星本身性质的重要工具。 相似文献
7.
本文借助于观测到的大、小麦哲伦云的星际尘埃辐射，估计总星系内的“冷”星际尘埃热再辐射对宇宙微波背景辐射的影响．结果表明：总星系内的星际“冷”尘埃的热辐射所形成的背景辐射对微波背景辐射的扰动强烈地依赖于宇宙减速因子和“冷”尘埃量，在宇宙背景探测者（ＣＯＢＥ）的观测结果的限制下，无论宇宙减速因子取何种值，“冷”尘埃所占的比例都是非常少的，如果Ｏｓｔｒｉｋｅｒ所作的平均每个星系内由尘埃产生的蓝光光深τＢ＝０．５的假定是合理的，那么星际尘埃量随温度的分布是非常不均匀的。 相似文献
8.
介绍了云南丽江高美古天文候选点,１９９５年１２月～１９９６年１１月全夜视宁度观测结果：全年平均ｒ０＝１６．５０ｃｍ（ＦＷＨＭ＝０．６７″）,夜平均极大值ｒｍａｘ＝２２．４１ｃｍ（０．４９″）,夜平均极小值ｒｍｉｎ＝１２．９５ｃｍ（０．８５″）。 相似文献
9.
给出并解释了星际介质中轻元素D，3He，4He和Li的最新观测数据．星际介质中轻元素的丰度观测结果可以用来检验标准大爆炸核合成理论，因此对这些元素的丰度研究具有重要的天体物理意义．到目前为止，轻元素丰度的观测结果基本上支持开放宇宙的观点．根据最新的观测结果，在本地星际介质中D丰度可能存在小尺度不均匀性，而对类星体吸收云的观测表明不同观测者所获得的原初D丰度结果最大差别可达一个量级．如果观测是可靠的，那么在目前的标准大爆炸核合成理论和星系化学演化模型框架下还不能解释这种结果．另外种种迹象表明太阳系丰度可能不代表45亿年前本地星际介质的丰度． 相似文献
10.
最近对哈勃常数的观测趋于一个大的值，引进宇宙学常数为主的宇宙学成了保持平坦宇宙并解决年龄矛盾的主要方法．本文讨论了（ｈ，Ω∧，ΩＭ）＝（０．８，０．８，０．２）的宇宙模型的一些后果，并和高红移椭球星系的观测，以及星系计数的观测作了比较．尽管观测事实表明Ω∧＝０．８模型比Ω∧＝０模型更具有优势，但这个结论仍是模糊的．除了年龄问题外，还不能排除（０．８，０，１）标准宇宙学的存在． 相似文献
11.
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
13.
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.
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.
__________
Translated from Astrofizika, Vol. 50, No. 3, pp. 355–368 (August 2007). 相似文献
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18.
V. Belokurov M. G. Walker N. W. Evans G. Gilmore M. J. Irwin M. Mateo L. Mayer E. Olszewski J. Bechtold T. Pickering 《Monthly notices of the Royal Astronomical Society》2009,397(4):1748-1755
We announce the discovery of a new Milky Way satellite Segue 2 found in the data of the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We followed this up with deeper imaging and spectroscopy on the Multiple Mirror Telescope (MMT). From this, we derive a luminosity of M v =−2.5 , a half-light radius of 34 pc and a systemic velocity of ∼−40 km s−1 . Our data also provide evidence for a stream around Segue 2 at a similar heliocentric velocity, and the SEGUE data show that it is also present in neighbouring fields. We resolve the velocity dispersion of Segue 2 as 3.4 km s−1 and the possible stream as ∼7 km s−1 . This object shows points of comparison with other recent discoveries, Segue 1, Boo II and Coma. We speculate that all four objects may be representatives of a population of satellites of satellites – survivors of accretion events that destroyed their larger but less dense parents. They are likely to have formed at redshifts z > 10 and are good candidates for fossils of the reionization epoch. 相似文献
19.
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
20.
V. A. Shefer 《Celestial Mechanics and Dynamical Astronomy》1990,49(2):197-207
A review is presented of the author's results on application of regularizing and stabilizing KS- transformation in the problem of investigation of the motion of unusual minor planets and comets. Two models of the motion of a minor body are considered, viz. the perturbed two body problem and the perturbed restricted three body problem. The variational equations in KS-variables and transformations for obtaining the matrix of partial derivatives of the instantaneous physical parameters of motion with respect to their initial values are presented. The peculiarities of the implementation of the algorithms developed as programs on a computer are described. The original results of the investigation of the efficiency of the developed algorithms and programs are discussed using as an example the motion of unusual minor planets Icarus and Geographos as well as comets Halley, Honda-Mrkos-Pajdusakova and Gehrels 3. 相似文献