Alpha Cygni as a radial-velocity variable

One hundred and twentythree radial velocities for α Cyg are derived between December 1977 and October 1982. These photospheric velocities are derived from N_I lines near 8700 å. Semiregular variations in radial velocities are present with periods of 7 to 20 days. The range of variation of 14.3 kms^?1 observed in the present radial velocities of α Cyg is close to the sum of the amplitudes (10.44 kms^?1) of all the pulsation periods from 7 to 101 days (Lucy 1976a) and is also approximately equal to micro and macro-turbulent velocities.     

The Edinburgh-Cape blue object survey

The Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B 18 in the southern sky. It is covering an area of sky of 10,000 square degrees with |b| > 30° and < 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric accuracy, the spectroscopic classification, and the completeness of the survey.     

The next generation stellar population synthesis library

Most of the analysis of absorption lines in galaxies is done in the Lick system, defined in the 1970's and 1980's by Faber, Burstein and collaborators. Working in this system is difficult, since it is based on low resolution spectra taken with a non-linear detector without flux-calibration. Due to intrinsic errors in the published indices the Lick system limits the accuracy with which one can analyse galaxy spectra. In the last 2 years we have observed a new stellar library to replace the Lick system. It consists of 1100 stars, covering a wide range in metallicity, abundance ratio, temperature and gravity, observed at a resolution of 2.0Å (9 for Lick) from 3500–7500Å, and calibrated in flux. With this library galaxy spectra can be analysed much more accurately than before, and in much more detail. Most important, the library now makes it possible to study absorption lines of galaxies at intermediate and high redshift, something which was impossible with the Lick system. With this library it will be possible for the first time to synthesise full Spectral energy distributions of galaxies in the optical based fully on observational spectra.     

地脉动在泉州市区地基土层场地评价中的应用

根据实际观测资料研究了泉州市区的地脉动特征以及脉动频谱特性与场地有关参数之间的关系。结果表明,地面脉动卓越周期的变化与场地土层构造有关,与场地工程地质条件的变化相对应。测试结果反映了地基土刚度(剪切波速)的变化与场地覆盖层厚度的大小有关。认为覆盖层厚度是影响地脉动卓越周期的重要原因。     

Sensitivity of the orbital content of a model stellar system to the potential approximation used to describe it

We have classified orbits in a stationary triaxial stellar system created from a cold dissipationless collapse of 100,000 particles. In order to integrate the orbits, two potential approximations with different fitting functions were used in turn. We found that the relative amount of chaotic versus regular orbits does depend on the chosen approximation of potential, even though both models resulted in very good fits of the underlying exact potential. On the other hand, the content of regular orbits, i.e., its distribution among main families, does not strongly depend of the potential approximation, being therefore a more robust signature of the gravitational system under study.     

转动恒星结构与演化研究

恒星的自转 ,是恒星结构和演化理论的难点。近年来有许多观测事实 ,特别是早型大质量星的观测事实 ,预示恒星的自转效应可能引起恒星内部的物质向外转移 ,造成恒星表面一些元素丰度超丰 ,并且对恒星结构和演化产生重要影响 ,因此 ,恒星的自转问题受到了越来越多的关注。考虑自转效应后 ,恒星结构和演化模型将是二维模型 ,本文综述了诸多作者如何将二维的恒星结构和演化模型简化为一维模型。作者在研究了以上作者的简化方法后 ,提出了一种比较简单的新方法。这种方法基于如下假设 :假设在等势面上的温度 ,密度 ,压强 ,光度 ,化学组成和角速度等物理和化学量近似于均匀分布 ,并且这些量与等价球面上的量相同。 (等价球面是假想的球面 ,它包围的体积与等势面包围的体积相等。)我们在等价球面上推出新的转动恒星结构和演化方程 ,构造出新的演化模型。这个模型与不考虑转动效应的演化模型相比 ,有以下变化 :流体静力学平衡方程变化 ;辐射温度梯度变化 ,并引起对流判据变化 ;星风物质损失和角动量损失增大。作为转动恒星结构和演化模型的应用 ,我们研究了中 ,小质量星中心氦燃烧阶段在赫罗图中的演化轨迹发生来回摆动 (又称为蓝回绕 )的物理机制问题。有诸多作者曾经研究了可以影响蓝回绕的各种因素。但是不知     

太阳短厘米波爆发中双重准周期脉动现象产生的可能机制

1990年5月23日0400—0451UT期间在遥隔两地的南大天文台与北师大天文台和北京天文台用时间分辨率1s和10ms分别在波长3.2cm、2cm和10.6cm上进行了太阳射电爆发的同时观测.发现了短厘米波爆发中的双重准周期脉动现象.本文根据这些观测资料连同S.G.D.发表的有关射电、光学和软X射线(SXR)耀斑等数据,提出了一个在耀(斑)环内非热与热辐射过程中由于相互作用而触发Alfven波和快磁声波的振荡模型,用来解释太阳短厘米波爆发中相关性很强的双重准周期脉动的起因和观测特征,并由此计算出爆发源区的平均物理参量T,N,B值。     

Gravitational potential energy of interpenetrating spherical galaxies in Hernquist’s model

Hernquist’s (1990) mass model for spherical galaxies and bulges described by the deVaucouleur’s profile gives analytical expressions for the density profile and the potential. These have been used to derive a simple and exact analytical expression for the gravitational potential energy of a pair of interpene-trating spherical galaxies represented by this model. The results are compared with those for polytropic and Plummer models of galaxis.     

Thermal-convective instability of a composite rotating plasma in a stellar atmosphere with finite larmor radius

Thermal-convective instability of a hydromagnetic, composite, rotating, inviscid and infinitely conducting plasma in a stellar atmosphere has been studied in the presence of finite Larmor radius. It is found that the criterion for monotonic instability holds good in the presence of the effects due to rotation and finite Larmor radius.     

An iras atlas of ysos in nearby dark clouds

We are using the newIRAS Sky Survey Atlas to construct a catalog of Galactic dark clouds and their associated Young Stellar Objects (YSOs). FromIRAS 100 and 60µm data we calculate images of the 100µm optical depth distribution in the clouds. Using theIRAS Faint Source Catalog we identify sources which have colors indicative of YSOs and have positions that lie inside cloud boundaries in the optical depth images. Here we present some preliminary results of applying this analysis to the Chamaeleon dark cloud complex.