太阳大气锂丰度的衰减

太阳大气锂的丰度７Ｌｉ／Ｈ＝１０－１１（按原子数计）。或［７Ｌｉ］＝ｌｏｇ（７Ｌｉ／Ｈ）＋１２＝１０．它比太阳系原始星云和银河系星际介质钾的丰度要低约两个数量级．因此太阳在它形成之后，其大气锂必定经受了严重衰减．然而年轻的银河疏散星团（如昂星团和英仙ａ星团）中有效温度高于５５００ Ｋ的主序星，其锂丰度都基本是正常的，井末呈现明显的衰减．这充分说明，太阳型恒星锂的衰减主要发生在主序阶段，而非在主序前的演化阶段． 在恒星中，７Ｌｉ是通过核反应７Ｌｉ（ｐ，ａ）４Ｈｅ，而毁坏．上述反应在Ｔ≥ ２．５×１０…     

Lithium depletion in G and K dwarfs

We present deep wide-field (16.4×16.4 arcmin²) Washington CT ₁ CCD surface photometry of the giant elliptical galaxy NGC 4472, the brightest member of the Virgo cluster. Our data cover a wider and deeper field than any previous CCD photometry. A single King model does not give a good fit to the surface brightness profiles of NGC 4472, but they can be fitted approximately using two King models: with the separate models representing the inner and outer regions . Surface brightness profiles for the outer region can also be fitted approximately by a de Vaucouleurs law. There is clearly a negative colour gradient within 3 arcmin of NGC 4472, in the sense that the colour gets bluer with increasing radius. The slope of the colour gradient for this region is derived to be Δ μ ( C − T ₁)=−0.08 mag arcsec⁻² for Δ log  r =1, which corresponds to a metallicity gradient of Δ[Fe/H]=−0.2 dex. However, the surface colour becomes gradually redder with increasing radius beyond 3 arcmin. A comparison of the structural parameters of NGC 4472 in C and T ₁ images has shown that there is little difference in the shapes of ellipses observed using isochromes or isophotes. In addition, photometric and structural parameters of NGC 4472 have been determined.     

Mass Loss in Young Stellar Objects

Various aspects of mass loss associated with Young Stellar Objects are reviewed. The classification of the driving sources of the outflows is presented, and the properties of the youngest sources, the Class 0 protostars, are given. The observed properties of the molecular, atomic, and neutral components of the bipolar flows are discussed and critically compared with the most recent theoretical models. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dust Formation and Mass Loss in Evolved Stars

The problem of dust formation in the circumstellar envelopes of Asymptotic Giant Branch stars is addressed. We summarize the basic thermodynamic prerequisites necessary to enable the formation and growth of solid particles from the gas phase and draw some conclusions on the evolution of the emergent dust component. In a circumstellar environment the dust grains interact with the stellar radiation field, which leads to a strong coupling among the local thermodynamic conditions and the dust formation process itself. By a consistent treatment of the physics describing the dust forming circumstellar shells of evolved stars we demonstrate, that the non-linear interaction among the dust formation process and the hydrodynamic and thermodynamic conditions of the dust forming system leads to a complex dynamical structure of these shells. Some observable consequences resulting from corresponding model calculations are given. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stellar Winds and Mass Loss in A-Type Supergiants

We examine the relationship between the surface escape velocities and wind terminal velocities of A-type supergiants according to the radiation-driven wind theory. This revised version was published online in July 2006 with corrections to the Cover Date.     

恒星绝热物质损失模型

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,     

Mass Loss and Circumstellar Dust Shells at T Tauri Stars

The mass loss of T Tauri stars leads to the production of dust in circumstellar space. The total amount of lost mass (and therefore of produced dust) is observed to be positiv correlated with the intensity of the H and Call emission lines of the objects. This fact is used in the present paper to explain quantitatively another correlation, namely the observation, that the interstellar extinction which is found by star counts in the wider surroundings of a T Tauri star is roughly proportional to the intensity of its Hα emission. By this, the outflow of circumstellar matter into the interstellar space seems to be observable directly.     

红团簇巨星的光谱分析及其作为I、K波段标准烛光的研究

基于高分辨率、高信噪比光谱观测资料，确定了19颗贫金属红团簇巨星的恒星大气参数，得到样本星4种α族元素(O、Mg、Ca、Si)的化学丰度．讨论了铁丰度与恒星大气参数的相关性以及α族元素丰度随金属丰度的变化，计算了共58颗红团簇巨星在I、K波段的绝对星等，讨论了它们与恒星铁丰度之间的关系．结果表明，在分析铁丰度范围内相对于I波段，K波段的绝对星等与铁丰度的相关性更弱，并且与利用理论模型得到的红团簇巨星I、K波段绝对星等与铁丰度的关系进行了比较与验证。     

On the Relations between Infrared Colors and Mass Loss Rates for S Stars

A relation between the infrared color K-[12] and the mass loss rate, dM/dt,is found for the intrinsic S stars. This relation is qualitatively similarto the ones for carbon stars and oxygen-rich Mira stars, but quantitativelydifferent. It could be useful in the context of the near infrared surveys,DENIS and 2MASS, which are in progress. Correlations between J-K and[12]–[25] indices and dM/dt are found to be loose for S stars.     

On the Role of Dust Mass Loss in the Evolution of Comets and Dusty Disk Systems

We present the results of an ongoing optical/thermal infraredphotometric imaging survey of thedust mass loss and nuclear size ofcomets. We find an evolution with time of the kind of dust emittedfrom a comet's surface. Our results indicate that the mass loss ratefrom the short period comets alone is enough to supply the interplanetary dust (IPD) complexagainst losses. We conclude that the nature of the IPD cloud haschanged over time, with small particles dominating early, and largerparticles dominating in the present era. The rate of destruction of short period (SP)comets due to sublimation mass loss is found to be low compared to therate of surface mantle formation, but fast compared to the rate of their dynamical removal from the inner solar system.     

Rapid oscillations of five stars in the spectral range G and K. II

The five stars HD 11112, HD 170747, HD 186651, HD 205390 and HD 224834 are a second group of objects enclosed in a larger observational programme for the search of rapid oscillations. They have been observed with the 50 cm photoelectrical ESO telescope at La Silla (Chile). For the star HD 205390 a variation of 163.8 min was found. The two objects HD 11112 and HD 186651 are suspected to be variable with periods of 139 min and 142.2 min and its overtones, respectively. But a verification of these results is necessary. For the last two objects HD 170747 and HD 224834 no variations were detected.     

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．     

Solar Models with Dynamic Screening and Early Mass Loss Tested by Helioseismic,Astrophysical, and Planetary Constraints

The faint young Sun paradox remains an open question. Presented here is one possible solution to this apparent inconsistency, a more massive early Sun. Based on the conditions on early Earth and Mars, a luminosity constraint is set as a function of mass. We examine helioseismic constraints of these alternative mass-losing models. Additionally, we explore a dynamic electron screening correction in an effort to improve helioseismic agreement in the core of the early mass-losing model.     

Molecules of Non-Photospheric Origin in Red Giants and Supergiants Revealed by the ISO SWS

Overall SEDs based on ISO SWS observations show fair agreement with photospheric model predictions for red (super)giant stars. However, some details of molecular spectra cannot be explained by a photospheric origin. In particular, fine structure in the H2O 2.7 μm band can be clearly resolved by the SWS and is identified in an early M giant, whose photosphere will never produce H2O. This is definite evidence for H2O of non-photospheric origin in an early M giant. Also, the observed H2O and CO2 bands in a late M giant are too strong to be explained by a photospheric origin alone. Further, the H2O 2.7 μm band is found in four early M supergiants in the h + χ Persei clusters (three of which show UIRs) and is especially strong in the M4 supergiant S Per (which also shows a highly peculiar SED). Thus, against a belief that H2O is found only in the latest M giants such as Miras, the SWS has revealed the presence of H2O in a wider region of the HR diagram. The origin of this H2O is unknown but is probably in a non-photospheric extra envelope. Such a H2O envelope appears to be a general feature through early M (super)giants to cool supergiants such as S Per, where the envelope has finally developed to be optically thick. This revised version was published online in August 2006 with corrections to the Cover Date.     

吸积盘边缘的质量和角动量损失与激变双星的演化

本文绘出了计算吸积盘边缘物质和角动量损失，以及它们对激变双星演化影响的理论模型.计算结果表明，紫外天文卫星（IUE）观测到的高速物质流是来源于吸积盘边缘，吸积盘边缘的角动量损失可以成为周期大于3小时的激变双星演化的物理机制．     

低部主序恒星锂和铍的衰减

根据化学非均匀恒星的非局部对流理论,计算了质量为0．7-1．15M(?)恒星主序演化模型锂和铍的衰减,并将理论和不同年龄疏散星团锂丰度的观测进行了比较．结果表明,贯穿对流混合能重现温度低于6400 K的晚型主序星锂丰度观测的一般性质．贯穿对流混合可能是晚型矮星锂衰减的一种重要机制．