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     

大质量双星非守恒演化

主要讨论建立大质量双星非守恒演化理论中的一些重要问题。     

星风对双星HD698运动的影响

本文利用变质量二体问题讨论了由于星风造成的质量减少对双星HD698的轨道的影响。     

受星风或膨胀气壳包围的双星物质损失率测定

对观测到的受星风或膨胀气壳包围的双星系统的PCyg谱线理论分析可精确测定其星风物质损失率．我们在计算这类星的理论谱线时，考虑了氢氦混合气体的多能级跃迁、轨道运动引起的密度非径向分布等因素，对轨道形状做了简化，所得结果是令人满意的．     

小质量密近双星Case A演化和几乎相接双星的形成

计算了总质量为3.9M,具有不同初始质比和两子星间距的一组模型在总质量、总角动量守恒假设下的Case A演化,以探求Case A演化与几乎相接双星(NCS)可能的联系.结果表明确实存在经过Case A质量交流演化为NCS系统的途径。并且这样形成的NCS系统其随后的演化有两种前景:一种随即演化为相接系统;另一种则经由慢速质量交流成为较稳定的半接或不接系统.但能够演化为NCS状态的初始模型范围极为狭窄,本文大致确定了它们的初始质比、子星间距等参量范围. 结合模型计算结果,对已知29个NCS系统作了统计研究,结果表明NCS系统与相接双星在演化上有很密切的联系.     

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     

中等质量恒星星风物质损失的机制

在考虑引力对星风物质损失的制约效果及辐射压与湍流压对其扰动效果的同时,通过引入可压缩流机制,考虑了恒星外壳对流区对星风物质损失的促进作用,从而建立了新的星风物质损失公式.之后,通过对3～5 M_⊙恒星理论模型的星风物质损失率计算,发现:从主序直至中心氦核燃烧结束阶段,新的星风物质损失公式计算所得星风物质损失率与经典星风物质损失公式计算结果几乎一致;而在TP-AGB阶段,应用新的星风物质损失公式计算的恒星模型则不受光度影响产生了持续的较大的星风物质损失,比较符合实际观测结果.     

Colliding Winds in Binary Star Systems: Theory, Models

The properties of the interaction region of colliding winds in hot star binaries and evolved low mass binaries are discussed in the frame of 2D and 3D hydrodynamical numerical simulations. The emission of such systems and their nebulae, in particular in X-rays, is reviewed and new results regarding orbital line profile variations are presented. The connection between colliding winds, thin shell instabilities and structure formation is outlined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydrodynamics of Supernova Evolution in the Winds of Massive Stars

Core-Collapse supernovae arise from stars greater than 8 M_⊙. These stars lose a considerable amount of mass during their lifetime, which accumulates around the star forming wind-blown bubbles. Upon the death of the star in a spectacular explosion, the resulting SN shock wave will interact with this modified medium. We study the evolution of the shock wave, and investigate the properties of this interaction. We concentrate on the evolution of the SN shock wave in the medium around a 35 solar mass star. We discuss the hydrodynamics of the resulting interaction, the formation and growth of instabilities, and deviations from sphericity.     

Asynchronous Rotation of a Massive Star in Close Binary Systems

Astrophysics - The problem of asynchronous rotation of massive stars in close binary systems is investigated in this paper. A massive star with twice the sun’s mass, a convective core, and an...     

The Evolution of Massive Close Binaries

We present results of evolutionary computations for massive close binaries with the Brussels simultaneous evolution code for conservative and non-conservative Roche lobe overflow (RLOF). We discuss mass transfer in massive close binaries during phases of RLOF, common envelope, spiral-in and merging. We examine the effects of stellar wind during successive stellar evolution phases and the final fate of primaries. We show how our library can be used to explain well-known binaries such as the WR + OB system V444 Cyg, HMXBs Vela X-1 and Wray 977, LMXBs like Her X-1, and binary pulsars. More details on the evolution of massive close binaries can be found in “The Brightest Binaries” (Vanbeveren et al., 1998).     

Novel Diagnostic of Shock Fronts in Low-Z Dense Plasmas

We performed an experiment using high-energy protons to characterize in situ the spatial and temporal evolution of a laser-driven shock propagating through a low-Z material. Radiography of the shock propagating through the low-Z transparent material (Lexan, quartz, diamond) enabled estimation of density under compression. In order to discriminate the influence of the shocked matter on the protons trajectory, a Monte-Carlo simulation was developed. This code describes the protons trajectory through the matter, calculating the scattering angle and the loss of energy.     

A Binary Evolution Model with Non-synchronous Rotations

By calculating the angular momentum transport during the evolution of a binary system, the variations of the rotational and revolution periods of the binary system under the tidal action, as well as the tidal effect on the evolution of the system are investigated. The calculated results indicate that when a close binary system evolves in the main sequence, the tidal friction will make the rotation and revolution approach to a closed state in a short time, but it takes a long time to attain a complete synchronization. After mass exchange started, the synchronous rotation can be changed more easily into the non-synchronous rotation for the semi-detached binaries. But for the contact binaries, the mass exchange is not strong enough to break the synchronization. The evolutionary tracks of the synchronization and non-synchronization models in the HR diagram are also compared with each other, and the result shows that for the non-synchronization model, the evolutionary curve of the primary star moves toward the direction of high luminosity and high effective temperature on the HR diagram at the mass exchange stage. Finally, by analyzing the statistical data of observations, it is found that the observed fact that the non-synchronous rotation exists in a period even longer than the tide-locking timescale can be explained by this model.     

GABE: Galaxy Assembly with Binary Evolution

We developed a new semi-analytic galaxy formation model: Galaxy Assembly with Binary Evolution(GABE). For the first time, we introduce binary evolution into semi-analytic models of galaxy formation by using the Yunnan-II stellar population synthesis model, which includes various binary interactions. When implementing our galaxy formation model onto the merger trees extracted from the Millennium simulation, it can reproduce a large body of observational results. We find that in the local universe, the model including binary evolution reduces the luminosity at optical and infrared wavelengths slightly, but it increases the luminosity at ultraviolet wavelengths significantly, especially in FUV band. The resulting luminosity function does not change very much over SDSS optical bands and infrared band, but the predicted colors are bluer, especially when the FUV band is under consideration. The new model allows us to explore the physics of various high energy events related to the remnants of binary stars, such as type Ia supernovae, short gamma-ray bursts and gravitational wave events, and their relation with host galaxies in a cosmological context.