共查询到20条相似文献，搜索用时 250 毫秒
1.
现今双星演化理论中,以子星的半么等于临界洛希瓣半径,作为双星中发生物质交换过程的判据,仅仅是一个为了将三维计算简化为一维计算而引入的近似判据,它在理论上不严格的。本给出了一个理论严格而又有一维计算的判据,并用新的判据和用子星半径等于临界洛希瓣半径的判据,对一个由９Ｍ⊙和６Ｍ⊙恒星组成的双星系统,进行了情况Ａ的演化计算。结果证明,用新的判据时,双星中发生物质交换过程的起始时间提前,快速物质交换过程 相似文献
2.
刘林 《中国天文和天体物理学报》1987,(3)
本文具体讨论了密近双星系统动力演化中洛希(Roche)临界等位面(即过第二直线秤动点的零速度面)所涉及到的零速度面的变化问题。考虑两子星相互绕转轨道偏心率e_1的影响时,在一定条件下,零速度面的变化并无长期项和周期特别长的共振项,而仅有一般周期项,其主周期即两子星相互绕转周期,这当然是可以理解的。所得结果可说明洛希模型具有一定的合理性,同时有可能更好地解释轨道偏心率e_1较大的密近双星系统的物质交换过程。 相似文献
3.
双星间的快速物质交换是一个非常复杂的过程,它涉及到双星演化的两个基本问题:物质交换的动力学不稳定性和公共包层的形成和演化.这两个问题是双星演化中最不清楚的两个基本问题.本论文通过建立相互作用双星之间的快速(绝热)物质损失模型,研究双星演化中物质交换的不稳定性判据和对公共包层的演化结局作出理论限制.利用恒星绝热物质损失模型得到的结果,还有很多潜在应用.比如,促进含双星的大样本恒星演化研究,改进演化星族合成方法等.恒星绝热物质损失模型的建立,基于主星在快速物质损失过程中,恒星内部的热量来不及交换, 相似文献
4.
黄润乾 《中国天文和天体物理学报》1997,(2)
本文研究了有碰撞星风激波存在的大质量双星系统的演化．碰撞星风激波存在的重要效应之一是产生Ｘ射线辐射，使有星风激波存在的大质量双星系统成为Ｘ射线双星系统的又一类新成员．碰撞星风激波存在的另一重要效应，是可以阻止双星系统中两子星之间的物质交换，因而对大质量双星系统的演化产生重要影响．对于一个由４０Ｍ⊙和３０Ｍ⊙组成的双星系统在情况Ｂ演化下，有星风激波存在与无星风激波存在两种情况相比较，前者的周期大大变短，系统的总质量大大减小． 相似文献
5.
潘开科 《中国天文和天体物理学报》1996,(3)
我们对前文（Ⅰ）和（Ⅱ）的实测和计算结果进行了统计分析，讨论了自转同步与相对半径、轨道周期间的关系．结果表明：几乎所有r＞0．18的不相接双星系统子星都是同步的，而r＜0．10的子星均处于非同步自转．在相接、半相接双星系统中，同步性与相对半径r也有很好的相关性，但由于子星间物质交流的影响，它们的同步性临界相对半径为0．21，大于不相接双星系统的0.18． 相似文献
6.
7.
密近双星自转的测量和研究（III）同步性的统计性质 总被引：1，自引：1，他引：0
我们对前（Ｉ）和（Ⅱ）的实测和计算结果进行了统计分析，讨论了自转同步与相对半径，轨道周期间的关系，结果表明，几乎所有ｒ〉０．１８的不相接双星系统子星都是同步的，而ｒ〈０．１０的子星均处于非同步自转，在相接，半相接双星系统中，同步性与相对半径ｒ也有很好的相关性，但由于子星间物质交流的影响，它们的同步性临界相对半径的０．２１，大于不相接双星系统的０．１８。 相似文献
8.
通过计算双星演化中的角动量转移,研究了潮汐作用下双星系统自转与公转周期的变化以及潮汐作用对双星演化的影响.结果表明,密近双星系统在主序演化时,潮汐摩擦会在较短的时间内使自转与公转达到比较接近的状态,此后经过一个较长时间的调整才能使自转与公转达到同步转动.物质交换阶段开始后,半相接双星系统更容易出现非同步转动,而相接双星系统物质交换很难破坏系统的同步状态.同时比较了非同步双星模型与同步双星模型演化曲线在赫罗图上的不同,结果表明非同步模型在物质交换阶段主星演化曲线向赫罗图光度和有效温度高的方向移动.最后通过对统计的观测数据进行分析后发现,采用该模型可以解释观测上双星超过潮汐锁定时标后仍然存在非同步转动的现象. 相似文献
9.
本文给出了首次食双星V375 Cas的BV两色光电测光资料和新的历元,并用Wilson-Devinney综合光变曲线方法取得测光解。结果表明:V375 Cas是一个类似RZ Dra的早型半相接双星系统,小质量子星充满了临界等位面,而大质量子星几乎充满了临界等位面,此星对于了解早型密近双星的演化是很有意义的。 相似文献
10.
本系统地研究了简并双星的形成,提出了简并双星形成的三种形成途径;稳定的洛希瓣物质交流－公共包层途径,公共包层－公共包层途径,核暴露－公共包层途径,并对简并双星的形成进行了Ｍｏｎｔｅ－Ｃａｒｌｏ模拟,探讨了模型参量（潮汐星风增强系数,稳定的洛希瓣物质交流过程中物质转移效率,双星初始质量比分布,公共包层抛射效率）对结果的影响,本模型成功地解释了简并双星的形成,解释了简并双星的质量分布,质量比分布和周 相似文献
11.
The accelerated expansion of the Universe was proposed through the use of Type-Ia supernovae （SNe） as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type-Ia SNe as standard candles rests on the assumption that their properties （and this correlation） do not vary with redshift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system, which forms a Quark-Nova Ia （QN-Ia）. The spin-down energy injected by the Quark-Nova remnant （the quark star） contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing QN-Ia are NOT constant in redshift. Simulated QN-Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We determine a correction between the true and fitted distance moduli, which when applied to Type-Ia SNe in the Hubble diagram recovers the ΩM = 1 cosmology. We conclude that Type-Ia SNe observations do not necessitate the need for an accelerating expansion of the Universe （if the observed SNe Ia are dominated by QNe Ia） and by association the need for dark energy. 相似文献
12.
Run-Qian Huang Han-Feng Song Shao-Lan Bi National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming Graduate University of Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(2):235-244
Three importantphysical processes occurringin contact binarysystems are studied. The first one is the effect of spin, orbital rotation and tide on the structure of the components, which includes also the effect of meridian circulation on the mixing of the chemical elements in the components. The second one is the mass and energy exchange between the components. To describe the energy exchange, a new approach is introduced based on the understanding that the exchange is due to the release of the potential, kinetic and thermal energy of the exchanged mass. The third is the loss of mass and angular momentum through the outer Lagrangian point. The rate of mass loss and the angular momentum carried away by the lost mass are discussed. To show the effects of these processes, we follow the evolution of a binary system consisting of a 12M and a 5M star with mass exchange between the components and mass loss via the outer Lagrangian point, both with and without considering the effects of rotation and tide. The result shows that the effect of rotation and tide advances the start of the semi-detached and the contact phases, and delays the end of the hydrogen-burning phase of the primary. Furthermore, it can change not only the occurrence of mass and angular momentum loss via the outer Lagrangian point, but also the contact or semi-contact status of the system. Thus, this effect can result in the special phenomenon of short-term variations occurring over a slow increase of the orbital period. The occurrence of mass and angular momentum loss via the outer Lagrangian point can affect the orbital period of the system significantly, but this process can be influenced, even suppressed out by the effect of rotation and tide. The mass and energy exchange occurs in the common envelope. The net result of the mass exchange process is a mass transfer from the primary to the secondary during the whole contact phase. 相似文献
13.
Lan-Wei Jia 《中国天文和天体物理学报》2008,8(4)
We analyzed a sample of 66 gamma-ray bursts (GRBs) and statistically confirmed the prediction on the time curve of the hardness ratio of GRBs made by Qin et al. based on the curvature effect. In their analysis, GRB pulses are divided into three types according to the shape of their raw hardness ratio (RHR) time curves, defined as to include the background counts to the signal counts, so as to make use of counts within small time intervals. Of the three types, very hard sources exhibit a perfect pulse-like profile (type 1), hard bursts possess a pulse-like profile with a dip in the decay phase (type 2), and soft bursts show no pulse-like profile but have only a dipped profile (type 3). In terms of the conventional hardness ratio, type 3 sources are indeed generally softer than those of type 1 and type 2, in agreement with the prediction. We found that the minimum value of RHR is sensitive in distinguishing the different types. We propose that GRB pulses can be classified according to the minimum value of RHR and that the different type sources may be connected with different strengths of the shock or/and the magnetic field. 相似文献
14.
Soft X-ray transients in the Hertzsprung gap 总被引：1，自引：0，他引：1
Ulrich Kolb 《Monthly notices of the Royal Astronomical Society》1998,297(2):419-426
15.
The pulsar timing residuals induced by gravitational waves from non- evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. We will analyze the various effects due to different parameters. The standard deviations of the timing residuals will be calculated with a variable parameter fixing a set of other parameters. The or- bits of the binary sources will be generally assumed to be elliptical. The influences of different eccentricities on the pulsar timing residuals will also be studied in detail. We find that the effects of the related parameters are quite different, and some of them display certain regularities. 相似文献
16.
17.
Since Baade's photographic study of M32 in the mid 1940s, it has been accepted as an established fact that M32 is a compact dwarf satellite of M31. The purpose of this paper is to report on the findings of our investigation into the nature of the existing evidence. We find that the case for M32 being a satellite of M31 rests upon Hubble Space Telescope (HST) based stellar population studies which have resolved red-giant branch (RGB) and red clump stars in M32 as well as other nearby galaxies. Taken in isolation, this recent evidence could be considered to be conclusive in favour of the existing view. However, the conventional scenario does not explain M32's anomalously high central velocity dispersion for a dwarf galaxy (several times that of either NGC 147, NGC 185 or NGC 205) or existing planetary nebula observations (which suggest that M32 is more than twice as distant as M31) and also requires an elaborate physical explanation for M32's inferred compactness. Conversely, we find that the case for M32 being a normal galaxy, of the order of three times as distant as M31, is supported by: (1) a central velocity dispersion typical of intermediate galaxies, (2) the published planetary nebula observations, and (3) known scaling relationships for normal early-type galaxies. However, this novel scenario cannot account for the high apparent luminosities of the RGB stars resolved in the M32 direction by HST observations. We are therefore left with two apparently irreconcilable scenarios, only one of which can be correct, but both of which suffer from potentially fatal evidence to the contrary. This suggests that current understanding of some relevant fields is still very far from adequate. 相似文献
18.
We obtain the chemical abundances of six barium stars and two CH subgiant stars based on the high signal-to-noise ratio and high resolution Echelle spectra. The neu- tron capture process elements Y, Zr, Ba, La and Eu show obvious overabundances relative to the Sun, for example, their [Ba/Fe] values are from 0.45 to 1.27. Other elements, in- cluding Na, Mg, A1, Si, Ca, Sc, Ti, V, Cr, Mn and Ni, show comparable abundances to the Solar ones, and their [Fe/H] covers a range from -0.40 to 0.21, which means they belong to the Galactic disk. The predictions of the theoretical model of wind accretion for bi- nary systems can explain the observed abundance patterns of the neutron capture process elements in these stars, which means that their overabundant heavy-elements could be caused by accreting the ejecta of AGB stars, the progenitors of present-day white dwarf companions in binary systems. 相似文献
19.
We propose a three-stage model with Blandford-Znajek (BZ) and hyperaccretion process to interpret the recent observations of early afterglows of Gamma-Ray Bursts (GRBs). In the first stage, the prompt GRB is powered by a rotating black hole (BH) invoking the BZ process. The second stage is a quiet stage, in which the BZ process is shut off, and the accretion onto the BH is depressed by the torque exerted by the magnetic coupling (MC) process. Part of the rotational energy transported by the MC process from the BH is stored in the disk as magnetic energy. In the third stage, the MC process is shut off when the magnetic energy in the disk accumulates and triggers magnetic instability. At this moment, the hyperaccretion process may set in, and the jet launched in this restarted central engine generates the observed X-ray flares. This model can account for the energies and timescales of GRBs with X-ray flares observed in early afterglows. 相似文献
20.
Rui Xue Maohai Huang 《中国天文和天体物理学报》2009,9(4)
A series of plane-parallel photodissociation region (PDR) models are calculated using the spectral synthesis code CLOUDY. These models span a wide range of physical conditions, with gas densities of n = 102 - 106 cm-3 and incident far-ultraviolet (FUV) fields of G0 = 100 - 106 (where Go is the FUV flux in units of the local interstellar value), which are comparable with various astrophysical environments from interstellar diffuse clouds to the dense neutral gas around galactic compact HII regions. Based on the calculated results, we study the thermal balance of PDR gas and the emissions of [ CII ], [ CI ] and [ OI ] fine-structure lines under different physical conditions. The intensities and strength ratios of the studied lines, which are frequently used as PDR diagnostics, are presented using contour diagrams as functions of n and Go. We compare the calculated PDR surface gas temperatures T8 with those from Kaufman et al. and find that Ts from our models are systematically higher over most of the adopted n-G0 parameter space. The predicated line intensities and ratios from our work and those from Kaufman et al. can be different by a factor greater than 10, and such large differences usually occur near the border of our parameter space. The different methods of treating the dust grain physics, the change of H2 formation and dissociation rates, and the improvement in the radiation transfer of line emissions in our CLOUDY models are likely to be the major reasons for the divergences. Our models represent an up-to-date treatment of PDR diagnostic calcula- tions and can be used to interpret observational data. Meanwhile, the uncertainties in the treatment of microphysics and chemical processes in PDR models have significant effects on PDR diagnostics. 相似文献