对具有最大曲率的广义相对论的Born—Infeld型修正

由于挠率与自旋的基本单位ｈ有关，空时拓扑的缺陷应当以Ｐｌａｎｃｋ长度的倍数出现，Ｐｌａｎｃｋ长度出自空时结构的内禀缺陷，这意味着Ｐｌａｎｃｋ长度是最小的基本长度，进而意味着有一个最大曲率存在。由此可得出一些物理结论：当坍缩物体接近其Ｓｃｈｗａｒｚｓｃｈｉｌｄ半径时，熵不会变为无穷大，而且我们还得出黑洞的最小质量（不为零且等于Ｍｐｌ），具有这一最小质量的黑洞可能在早期宇宙中形成，或作为较大的黑洞在     

超弦理论中的宇宙波函数

本文讨论了超弦理论中的宇宙波函数，使用Ｖｉｌｅｎｋｉｎ的边界条件，我们得到了膨胀子场Ｄ的值给定时宇宙标度因子ａ的几率分布。我们还得到了宇宙自发成核时，经典宇宙的标度因子的最小值为Ｐｌａｎｃｋ长度的数量级，这说明量子效应能阻止宇宙塌缩到奇点。     

黑洞附近吸积流的稳定性研究

本文采用了多方物态方程ｐ＝ｋρ＾（１＋１／ｎ）研究了在黑洞附近跨声速α吸积盘的径向线性稳定性，在导出扰动色散关系时考虑了吸积流的径向运动速度，结果表明粘滞系数α存在一上限αｃ，当α＞αｃ时，吸积流是不稳定的，αｃ与多方指数ｎ及吸积流的径向速度ｖｒ有关。     

黑洞吸积盘内边缘半径的演化

本文用广义相对论讨论了黑洞吸积盘内边缘半径ｒ（ｍｓ）的演化规律。结果表明，吸积盘的中心黑洞在由Ｓｃｈｗａｒｚｓｃｈｉｌｄ型向极端Ｋｅｒｒ型演化的过程中，黑洞的角动量变化对ｒ（ｍｓ）的影响始终比黑洞的质量变化对ｒ（ｍｓ）的影响大。在此过程中ｒ（ｍｓ）始终是连续、单调减小的。本文得出ｒ（ｍｓ）对时间变化率的取值范围，并对其物理意义作了讨论。     

黑洞熵可以量子化吗?

在黑洞蒸发的最后阶段其残余质量为Planck质量的量级,因而所对应的黑洞熵为2πk_B量级,在Bekenstein工作的基础上作者导出在吸积物质的过程中黑洞的最小熵增为2πk_B,这一最小熵增又限制能参与吸积物质的黑洞的质量下限为Planck质量的量级,因而所对应的最小黑洞熵也为2πk_B这一量级。作者进一步指出:黑洞的最小熵及最小熵增不受引力常数G变化的影响,因此上述结论在极早期宇宙中也能成立,在上述分析的基础上作者提出一个猜想:黑洞熵可以量子化,其量子单位为2πk_B。     

新闻速递

拥有超大质量黑洞的最小星系 使用美国宇航局的哈勃空间望远镜,天文学家发现—个超大质量黑洞出现在了一个十分不可能的地方。对超致密矮星系M60-UCD1的观测显示,在其中心存在一个超大质量黑洞,由此使得它成为了拥有超大质量黑洞的最小星系。这说明可能还有更多的超大质量黑洞被错过了,它们对于大质量星系的形成会具有重要的意义。     

星系的转动与黑洞形成的判据

本文通过数值计算解出稳态星系模型，并与椭圆星系及旋涡星系核球的自转和弥散速度曲线相比较。由星系运动曲线拟合出的星系半径与从光度曲线拟合出的潮汐半径不一致，后者总是前者的３倍左右，这是由于分布函数的截断方式不妥造成的。我们的结论是：该模型虽不能正确描述整个星系，但却能正确描述星系的较内部区域，我们分析了三个有速度曲线资料的星系黑洞候选者：Ｍ１０４、Ｍ３１和银河系，发现它们由于有太快的自转，都不可能在达到稳态之后有满足形成黑洞所要求的≡ｃＪ／ＧＭ２＜１的区域存在，因此它们的中心如有黑洞，只能有更早的起源。     

Bianchi型宇宙的量子化

本文将Ｗｈｅｅｌｅｒ—ＤｅＷｉｔｔ方程的平方根形式用于具有辐射场源的Ｂｉａｎｃｈｉ—Ⅰ型宇宙组成的微超空间模型，由此导出一个具有守恒流和正定几率密度的宇宙波函数．本文探讨了Ｂｉａｎｃｈｉ型宇宙的３次量子化，把类似于弯曲时空中量子场论程序应用到各向异性的Ｂｉａｎｃｈｉ—Ⅲ型宇宙中，给出了Ｗｈｅｅｌｅｒ—ＤｅＷｉｔｔ方程所满足的宇宙波函数解．把波函数作为微超空间中宇宙场算符看待后，不仅能解决量子宇宙学中几率解释的困难，而且也能得到宇宙多次产生的结论．同时估算了各种宇宙从“无”产生平均数目，给出了宇宙生成的分布，发现它遵从Ｐｌａｎｃｋ分布．     

BL Lac天体PKS 2155－304的X射线谱

对ＢＬＬａｃ天体ＰＫＳ２１５５－３０４的多波段同时性观测表明，１－１０ｋｅＶ左右的Ｘ射线谱可用近似幂律谱和６－７ｋｅＶ之间的吸收峰很好地描述，观测到的光变时标，秒。这说明ｘ射线很可能是产生于中心黑洞附近的内部区域而穿过源外部“冷”的气体到达观测者的，因此，本文假定１－１０ｋｅＶ左右的Ｘ射线是在中心天体附近区域产生，观测到的谱则是原始谱在穿过周围较“冷”的等离子体介质时，受到康普顿软化所致。由此可解释Ｘ射线谱的观测特征，特别是Ｘ射线幂律谱高频端的陡化。     

高红移大质量星系的形成与演化

星系形成及演化一直是天体物理研究中最重要的领域之一.近10 yr来星系形成及演化的研究取得了突破性进展,主要包括:(1)近邻星系在颜色-星等图上呈现双峰分布,早型星系普遍颜色较红,而晚型星系颜色偏蓝;并且近邻宇宙红星系的总质量相对于红移z=1时至少增长了1倍,意味着存在蓝星系到红星系的转化过程.这一转化过程是如何发生的成为现代星系形成演化领域最重要的问题之一;(2)星系中心超大质量黑洞质量跟核球质量有很强的相关,意味着黑洞演化跟星系演化有着紧密的关系.黑洞的活动(活动星系核)如何影响星系演化也成为了亟待解决的问题之一.然而近邻宇宙中的大质量星系基本都已停止了剧烈的恒星形成活动和黑洞活动,因此,要回答这些问题,我们需要仔细研究宇宙早期红移在z≈2的星系性质.在这一红移处,星系中的恒星形成和黑洞增长均处于高峰期.     

A survey of orbits of co-orbitals of Mars

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.     

Equation of state and anisotropy of pressure of magnetars

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.     

Estimation of the Time Scale of Merging of the Components of Contact Binaries of the W UMa Type

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.     

淮河洪水的可公度性分析

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。     

Flattening of galaxies of different morphological types in subclusters of Coma

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).     

基于STK的寿命末期GEO卫星轨道演化分析

地球同步轨道上的GEO卫星接近寿命末期时,星上的有效载荷和电子元器件等仍能正常应用,此时如果只做东西方向的位置保持,可以大幅度延长卫星的在轨工作寿命。简要介绍了引起GEO卫星轨道变化的主要摄动力,利用STK软件分析寿命末期GEO卫星的运动规律,并给出这类GEO卫星轨道演化的仿真分析流程,用以指导寿命末期GEO卫星的开发应用工作。     

The discovery of Segue 2: a prototype of the population of satellites of satellites

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.     

Investigation of Times of Minima of Selected Early-Type Eclipsing Binaries

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.     

Application of KS-transformation in the problem of investigation of the motion of unusual minor planets and comets

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.