Ba星系统的星风吸积及污染因子

用整个系统的角动量守恒条件代替切向动量守恒条件,且δr ≠ 0,考虑轨道偏心率的高次项,推导了星风吸积质量及轨道参量变化方程.在此基础上计算了 Ba星系统在星风吸积过程中吸积的物质量和轨道参量的变化,并讨论了影响Ba星污染因子的 因素.     

Ba星系统轨道参量的变化

考虑到δｒ≠０，用整个系统的角动量守恒条件代替切向动量守恒条件，推导了星风吸积质量及轨道参量变化方程，在此基础上计算了Ｂａ星系统在星风吸积过程中吸积的物质量和轨道参量的变化，并讨论了逃逸物质附加切向速度对各参量的影响。     

外赋AGB星星风吸积的轨道参量变化方程

用整个系统的角动量守恒条件代替切向动量守恒条件,将星风吸积与盘吸积两种质量吸积一起来,考虑双星系统的轨道偏心率ｅ的二次以上的高次项,重新推导了吸积质量及轨道参量变化方程。     

钡星星风吸积模型的检验

考虑δr≠0和偏心率e二次以上的高次项,采用星风质量吸积的角动量守恒模型,并根据由此模型推出的星风吸积质量及轨道参量变化方程,重新计算了ζCap系统在星风吸积过程中吸积的物质质量和轨道参量的变化,从而进一步证实在分离双星系统,钡星通过星风吸积模型与其伴星发生了质量传输.     

潮汐作用与外赋AGB星系统的轨道根数变化

用整个系统的角动量守恒条件代替切向动量守恒条件，考虑双星系统的轨道偏心率e的二次以上的高次项，并且考虑潮光作用对轨道根数变化的影响，重新推导了轨道根数变化的方程。     

外赋AGB星质量吸积的角动量守恒模型：方程的推导

考虑到δｒ≠０，用整个系统的角动量守恒条件代替切向动量守恒条件，将星风吸积与盘吸积两种质量机结合起来考虑，推导了吸积质量及轨道参量的变化方程。     

两个星风吸积模型的比较

利用KOMIYA和LIU的2个星风吸积模型计算了富碳极贫金属星(CEMP星)和CH星表面C丰度与轨道周期P终值的关系、污染因子R同轨道周期P终值的关系,以及轨道半长轴A随伴星质量M2的变化。从而对2个星风吸积模型进行了比较。从计算结果可以看出,2个星风吸积模型是一致的。     

钡星s-元素丰度的研究

采用角动量守恒的星风吸积模型,计算了5颗钡星的重元素丰度,并和观测结果作了比较.探讨了钡星的形成机制和中子俘获在重元素核合成方面所起的主导作用,及金属丰度对强钡星和弱钡星形成的影响.     

大偏心率椭圆轨道星上轨道外推的参数化模型

众所周知,数值方法和分析方法都可以用于轨道预报.一般而言,采用数值方法可以获得更高的精度,采用分析方法可以达到更高的效率.对于近圆轨道卫星,已有许多成熟的数值方法和分析方法可以用于轨道预报.而对于大偏心率椭圆轨道卫星,这些方法都有各自的局限性.传统的数值积分器工作效率较低;分析方法中多采用简化的力模型,因而可以达到的精度有限.为实现大偏心率椭圆轨道卫星的星上轨道预报,本文提出了一种解决方案.其核心思想是基于摄动分析解的表达式,尝试构造拟合公式,用不同的频率项反映摄动影响下轨道根数的周期变化和长期变化.最终以拟合和计算的过程代替求解微分方程,建立参数化模型,从而实现轨道外推.应用此模型时,将首先通过拟合公式对真近点角f、近点角距ω、升交点经度Ω、轨道倾角i和地心距r进行拟合与计算,然后利用这5个轨道根数计算出卫星在惯性坐标系下的位置矢量,得到最终的预报结果.为检验方法的可行性,本文利用该参数化模型对33颗闪电轨道卫星进行了轨道外推.对每颗卫星分别进行28组试验,每组算例的外推弧段为3天.数值试验结果表明,轨道根数f,ω,i与r的计算结果受到轨道偏心率的影响.3天内,轨道外推的位置精度一般约为百米级.     

强钡星和弱钡星的比较

利用星风吸积模型,计算了钡星的初始质量和AGB伴星的金属丰度对弱钡星和强钡星超丰因子的影响,计算了弱钡星和强钡星重元素(Y,Nd)丰度随轨道周期终值的变化,并和观测值作了比较.由此得出结论:强钡星和弱钡星的区别主要是金属丰度不同(即年代不同),而不是轨道距离;弱钡星和强钡星相比,属于较年轻、质量较大、金属丰度较丰富的星族;这就意味,s-元素的核合成在低金属丰度星族更有效产生.     

Circumbinary disk, an efficient medium extracting orbital angular momentum in close binaries

The loss of orbital angular momentum plays an important role in the mass transfer and orbital evolution of close binaries. The traditional mechanisms of orbital angular momentum loss consist of gravitational wave radiation, mass loss and magnetic braking. However, a small fraction of the mass outflow may form a thin circumbinary disk (CB disk) located in the orbital plane of the binary during mass exchange. The tide torques caused by the gravitational interaction between a CB disk and a binary system brake binary effectively, and extract the orbital angular momentum from the binary system. In this study, numerical calculations for the evolution of the white dwarf binary show that a CB disk is an efficient medium extracting orbital angular momentum even if the mass loss is very small. Finally, some theoretical research and observational progress on CB disks are presented. Supported by the National Natural Science Foundation of China (Grant Nos. 10873011, 10573009, 10573010) and Program for Science & Technology Innovation Talents in Universities of Henan Province, China     

Two populations of X-ray pulsars produced by two types of supernova

Two types of supernova are thought to produce the overwhelming majority of neutron stars in the Universe. The first type, iron-core-collapse supernovae, occurs when a high-mass star develops a degenerate iron core that exceeds the Chandrasekhar limit. The second type, electron-capture supernovae, is associated with the collapse of a lower-mass oxygen-neon-magnesium core as it loses pressure support owing to the sudden capture of electrons by neon and/or magnesium nuclei. It has hitherto been impossible to identify the two distinct families of neutron stars produced in these formation channels. Here we report that a large, well-known class of neutron-star-hosting X-ray pulsars is actually composed of two distinct subpopulations with different characteristic spin periods, orbital periods and orbital eccentricities. This class, the Be/X-ray binaries, contains neutron stars that accrete material from a more massive companion star. The two subpopulations are most probably associated with the two distinct types of neutron-star-forming supernova, with electron-capture supernovae preferentially producing systems with short spin periods, short orbital periods and low eccentricities. Intriguingly, the split between the two subpopulations is clearest in the distribution of the logarithm of spin period, a result that had not been predicted and which still remains to be explained.     

关于两电流元之间相互作用的探讨

一般情况下,两电流元间相互作用力是不满足牛顿第三定律的,从而两运动的带电粒子在电磁力相互作用下,它们的机械动量是不守恒的.在考虑到运动的带电粒子的机械动量的同时,也考虑到电磁场的能量和动量,从而证明了,在运动的带电粒子和电磁场组成的系统中动量仍然是守恒的.     

密近双星的Roche势的计算

文章对密近双星的Roche势进行分析,并计算出3个内、外拉格朗日点及其相应的Roche势.根据Roche势对密近双星进行分类,这对于探寻3类密近双星的演化联系起重要作用.当子星充满内(或外)临界等势面必定会发生质量和角动量的转移或损失,从而引起质量和角动量在两子星间的重新分布并最终导致双星并合.Roche势的计算对于密近双星的观测、分析和研究具有重要意义.     

Transiting circumbinary planets Kepler-34 b and Kepler-35 b

Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289?days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131?days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ～1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.     

An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system

The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are rather low, because we know of only a few double-neutron-star binaries with merger times less than the age of the Universe. Here we report the discovery of a 22-ms pulsar, PSR J0737-3039, which is a member of a highly relativistic double-neutron-star binary with an orbital period of 2.4 hours. This system will merge in about 85 Myr, a time much shorter than for any other known neutron-star binary. Together with the relatively low radio luminosity of PSR J0737-3039, this timescale implies an order-of-magnitude increase in the predicted merger rate for double-neutron-star systems in our Galaxy (and in the rest of the Universe).     

Evidence for planet engulfment by the star HD82943

Current models of the evolution of the known extrasolar planetary systems need to incorporate orbital migration and/or gravitational interactions among giant planets to explain the presence of large bodies close to their parent stars. These processes could also lead to planets being ingested by their parent stars, which would alter the relative abundances of elements heavier than helium in the stellar atmospheres. In particular, the abundance of the rare 6Li isotope, which is normally destroyed in the early evolution of solar-type stars but preserved intact in the atmospheres of giant planets, would be boosted substantially. 6Li has not hitherto been observed reliably in a metal-rich star, where metallicity refers to the total abundance of elements heavier than helium. Here we report the discovery of 6Li in the atmosphere of the metal-rich solar-type star HD82943, which is known to have an orbiting giant planet. The presence of 6Li can probably be interpreted as evidence for a planet (or planets) having been engulfed by the parent star.