大质量双星系统的非守恒演化

由于大质量双星系统有强大的星风物质损失,因而在研究其结构和演化时必须考虑星风物质损失,动量损失,物质交换以及由以上原因引起的轨道参量的变化,此外,天文观测又证实,一些大质量双星系统中存在星风冲击波,有Ｘ射线辐射以及有致密天体（白矮星,中子星）的存在,因此在研究大质量双星的演化时,又会遇到在星风冲击波理论及其对演化的影响,双星系统何时会演化成为公共外壳的系统,以及双星系统中如果发生超新星爆发,是否会     

AGB星的超星风与热脉动的研究

至今国际上对ＡＧＢ星的超星风、热脉动及振动的理论研究工作中都忽略了湍流压的存在，然而对于一个整个外壳都处于完全对流的ＡＧＢ星，湍流压是存在的，并且由于湍流压的存在将对气体压强、密度、温度以及各热力学量产生影响，因而对ＡＧＢ星的超星风、热脉动及振动产生影响。本文以恒星结构演化理论中常用的混合程对流理论为基础，给出了湍流压以及考虑湍流压情况下恒星内部物态方程和各热力学量的表达式，并给出了判别恒星外壳产生动力学非稳定性的判据，并在此基础上研究了质量为２．８Ｍ⊙和７Ｍ⊙的恒星从主序到ＡＧＢ星的演化。目的是研究有湍流压情况下ＡＧＢ星的超星风及热脉动的机理。结果表明，对于７Ｍ⊙恒星，在红巨星及ＡＧＢ阶段，湍流压可以达到总压强的３０％，并且对恒星的结构产生重要影响，对于２．８Ｍ⊙恒星，在红巨星及ＡＧＢ阶段影响较小。由于湍流压的作用，２．８Ｍ⊙和７Ｍ⊙恒星在ＡＧＢ阶段和红巨星阶段，靠近表面的区域会出现动力学非稳定性，造成物质向外喷流，这就是ＡＧＢ星和红巨星产生强大星风的物质损失的原因。研究还表明，湍流压效应造成７Ｍ⊙ＡＧＢ星的氢燃烧壳层产生主周期为５０年的脉动现象，同时使氦燃烧壳层的热脉动提前发生和周期变短     

激变双星的角动量损失机制和演化

本详细研究了激变双星系统的演化，发现磁制动机制导致的角动量损失要求星风的量级为１０＾－１１—１０＾－１２Ｍ⊙ｙｒ＾－１，这比太阳风强１０＾２－１０＾３倍，表明磁星风机制失效。作认为驱动双星系统演化的角动量损失是由来自致密星的吸积盘外边缘的物质溢出的惯性离心力所致。     

钡星的形成机制(Ⅱ)Monte Carlo分析

本文对文章Ⅰ所建立的钡星形成的完备模型进行了ＭｏｎｔｅＣａｒｌｏ分析，并同观测结果作了比较．结果表明，大部分强钡星可能产生于星风吸积过程、星风暴露过程和稳定的洛希瓣物质交流过程，而大部分中等钡星可能产生于星风吸积过程和星风暴露过程．银河系中钡星的数量、轨道周期分布和质量函数分布在本文各种模型计算结果范围之内．模型还预言钡星轨道周期与污染因子相关．模型给出，银河系中钡星的诞生率为００２／年左右，亮于１０个星等的钡星大约有６０００颗，强钡星的平均质量为１８Ｍ⊙左右，而钡星的白矮星伴星平均质量为０６０Ｍ⊙．另外，结果还显示，星族ＩＡＧＢ星热脉动开始较早，星风有潮汐增强效应存在（Ｂ～５００），ｓ过程最大恒星质量为２Ｍ⊙左右．     

激变双星的磁滞效应

本文研究了激变双星中较冷次星的星风在磁场耦合作用下造成的角动量损失，以及对激变双星演化的影响。本文特别注意到双星成员的星风物质损失和角动量损失应该与单星情况明显不同，这就是：双星成员的星风物质损失受到潮汐效应和系统自转效应的影响而增大，同时双星成员的角动量是由轨道角动量和自转角动量所组成，并且轨道角动量远大于自转角动量。研究结果表明，由于次星的星风物质损失率很小，星风的速度也不大，因而磁滞效应造成的角动量损失极小，不能成为驱动周期大于３小时的激变双星演化的机制。     

NGC 3603星团中的大质量逃逸双星

非团环境中的大质量恒星以及大质量双星的起源是理解大质量恒星形成和演化的关键问题之一. 年轻大质量星团内的动力学交会过程是产生大质量逃逸星的重要途径之一. 选取了银河系内年轻大质量星团NGC 3603外围的两个碰撞星风系统候选体MTT68A和MTT71作为研究对象, 通过分析\emphChandra X射线观测以及\emphGaia第2批数据发布(DR2)中的天体测量结果, 研究它们作为相互作用的大质量双星系统的起源. X射线数据的分析表明, 它们的X射线能谱中存在Fe XXV发射线成分; 相较于普通O型星, 以双温等离子体模型拟合得到偏高的高温成分温度($\gtrsim$2.0keV), 并且X射线光度与热光度的比值也较高($\gtrsim10^{-5.8     

激变双星的磁滞效应

本研究了激变双星中较冷次星的星风在磁场耦合作用下造成的角动量损失，以及对激变双星演化的影响。本特别注意到双星成员的星风物质损失和角动量损失应该与单星情况明显不同，这就是：双星成员的星风物质损失受到潮汐效应和系统自转效应的影响而增大，同时双星成员的角动量是由轨道角动量和自转角动量所组成，并且轨道角动量远大于自转角动量。研究结果表明，由于次星的星风物质损失率很小，星风的速度也不大，因而磁滞效应造成     

外赋AGB星星风吸积的角动量守恒模型

用整个系统的角动量守恒条件代替切向动量守恒条件,推导出星风质量吸积及轨道参量变化方程．在新的轨道参量变化方程的基础上,计算了外赋AGB星系统的星风质量吸积及轨道参量的变化．将星风吸积模型同内禀AGB星核合成模型结合起来,通过逐次脉冲吸积质量和混合,自洽地计算外赋AGB星的重元素超丰,并给出计算结果与观测值的比较．对初始质量较大的Ba星（M2．0＝2．5M⊙）,当系统轨道周期大于1300天时,属于星风吸积,小于600天成为共同包层双星或灾变双星．对初始质量较小的Ba星（M2．0＝13M⊙）,当系统轨道周期大于1600天时,属于星风吸积,小于600天时成为灾变双星,由此可以解释Ba星的重元素超丰和轨道参量的观测事实,并有利于解释观测到的外赋S星轨道周期的600天下限．随着星风吸积过程的进行,轨道偏心率逐渐增大,这对解释Ba星轨道偏心率平均值大于外赋S星和CH星平均值的观测事实有利．     

钡星系统轨道根数分布及丰度的Monte-Carlo模拟计算

采用星风质量吸积的角动量守恒模型，用Monte—Carlo方法研究了普通红巨星双星系统和钡星的轨道根数的变化规律，由于钡星系统是由普通红巨星双星系统演化而来，因此钡星系统的轨道偏心率及周期的分布显示了经过质量吸积后双星系统的最终轨道特征。计算结果表明，随着星风吸积过程的进行，在星风质量损失阶段系统轨道半长轴将增大，导致轨道周期增大，而偏心率变化不大，由此可以解释普通红巨星双星系统和钡星系统的轨道根数的分布规律和变化情况以及钡星重元素丰度分布特征。     

激变双星的角动量损失机制和演化

本文详细研究了激变双星系统的演化，发现磁制动机制导致的角动量损失要求星风的量级为１０￣（－１１）－１０￣（－１２）Ｍ＿⊙ｙｒ￣－１，这比太阳风强１０￣２－１０￣３倍，表明磁星风机制失效，作者认为驱动双星系统演化的角动量损失是由来自致密星的吸积盘外边缘物质溢出的惯性离心力所致。     

Acceleration of Numerical Integration of the Equations of Motion of Asteroids

Solar System Research - Finding and studying possible collisions of asteroids approaching the Earth requires a significant amount of computation. This paper describes the R0 program created to...     

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.     

Observations of the intensity of the penumbra of sunspots

Observations of the penumbral intensity of sunspots in 13 wavelength regions are presented. In 4 wavelength regions 54 sunspots are measured. In the other wavelength regions the number of sunspots considered ranges from 3–19.The penumbral intensity alters with position within the spot. This intensity variation is found to be comparable with the change in intensity from one spot to another. The penumbral intensity is found to be independent of spot size in the sample considered.The penumbra model of Kjeldseth Moe and Maltby (1969) with = 0.055 is supported by the measurements.     

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.     

Graphical representation of periodic motion of the line of nodes of the Moon

In the text-books of astronomy, sections generally related to the Moon deal with the orbital elements of the Earth-Moon system such asa, e, i, , and the time of perigee passage. While the MEAN of the first of the three elements do not vary, mean longitude of the ascending node-mean longitude of the lunar perigee and the time of perigee passage undergoes secular as well as periodic changes due predominantly to the action of the Sun's gravitational attraction. While to a certain degree, explanations related to the calculation of the lunar orbit parameters are given, not a single graphical representation of these short- or long-periodic changes are presented. We allow the number of data related to these periodic changes must cover a large span of time; and if regression of the line of nodes or advances of the line of apses are to be graphically seen, data covering 18.61 and 8.85 yr, respectively, are needed. In this work we particularly aim at the graphical representation of the periodic changes of the line of nodes.