Spectral Observations of BIG Objects. III

Results of spectral observations of 66 objects from the BIG (Byurakan IRAS Galaxies) sample made with the 1.93 m telescope at the Observatoire de Haute Provence (OHP, France) are presented. Emission lines are observed from 64 of the galaxies. The red shifts are determined, the radial velocities, distances, and absolute stellar magnitudes are calculated, the spectrum line parameters are determined, diagnostic diagrams are constructed, the objects are classified according to activity type, and their IR and far-IR luminosities are calculated. Of the 66 objects (corresponding to 61 IRAS sources), 6 are Sy2, 2 are LINERs, 8 are AGN (Sy2 or LINER), 10 are composite, 34 are HII, and 4 are Em of undetermined type. It is calculated that IRAS 07479+7832= BIG d141a is a ultraluminous IR galaxy (ULIG), and 21 are LIG. Spectra of several of the galaxies being studied are presented.     

Variable stars in the globular cluster NGC 6362

We report the results of a CCD search for short-period variables in the field of a southern globular cluster NGC 6362. We identified 19 new candidate variables, five of which are cluster RR Lyraes, four are probable SX Phe-type stars and eight are eclipsing binaries. Of the discovered binaries, three are EA-type systems, two of which are located on the cluster CMD in the turn-off region and the third 1 mag above the turn-off point, in the yellow straggler region. Five other systems are of W UMa type, three of which are foreground objects and two are likely cluster members. The remaining two candidates exhibit a modulation of the brightness level with an amplitude of 0.1–0.2 mag; further observations are needed to reveal the nature of their variability. Phased VI light curves for 20 variables (18 RR Lyrae stars and two blue stragglers) located in the central region of the cluster are presented.     

Flows in clumpy planetary nebulae

The dynamics of clumps observed in planetary nebulae are considered. The possibility that SiO maser spots in evolved stars and the planetary nebula clumps are formed by the Parker instability behind shocks in pulsating stars' atmospheres is raised. Molecular observations of the clumps are suggested. The effects of the ablation of clumps on the global flow structure of a more tenuous plasma in which they are embedded are reviewed.     

Spectral study of BIG objects on the 2.6-m telescope at the Byurakan astrophysical observatory

Results of spectral observations of 45 objects from the BIG sample (corresponding to 35 IRAS sources) obtained on the 2.6-m telescope at the BAO are reported. Emission lines are observed for 42 galaxies, 1 object is an absorption galaxy, and 2 turned out to be stars. The red shifts are determined, the radial velocities, distances, sizes, and absolute stellar magnitudes are calculated, the parameters of the spectral lines are determined, the objects are classified according to their activity type, and the IR and far IR luminosities are calculated. Of the 42 emission galaxies, 1 was type Sy2, 2 were LINERs, 1 was an AGN (Sy2 or LINER), 4 were composite, 25 were HII (including 6 with nuclear star-formation activity), and 9 were Em of undetermined type (3 of which may be AGN). Calculations show that 23 of the objects are LIG. A physical coupling is discovered for 9 multiple systems. Spectra of some of the galaxies are shown. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 23–40 (February 2006).     

Three-dimensional bifurcations of periodic solutions around the triangular equilibrium points of the restricted three-body problem

Vertically critical, planar periodic solutions around the triangular equilibrium points of the Restricted Three-Body Problem are found to exist for values of the mass parameter in the interval [0.03, 0.5]. Four series of such solutions are computed. The families of three-dimensional periodic solutions that branch off these critical orbits are computed for µ = 0.3 and are continued till their end. All orbits of these families are unstable.     

恒星临边昏暗系数的测定

介绍一种新的一级挖和二级近似描述恒星大气临边昏境现象方法,其临边昏境系数可通过有关物理量的直接测量或测量流量和辅助量恒星表面温度的方法间接给出。与太阳观测比较和数值模型大气方法比较,均显示新方法能够以很精确的方式描述恒星临边昏境关系,或确定其相应系数 方法对太阳观测的１７６个数据比较了统计方差,其中直接法的一级挖和二级挖分别为０．３８％和０．２６％;间接法的方差与此相近而略大;与数值模型大气比较其     

Dense star clusters as the sources of gamma-ray-burst progenitors

Two independent sets of arguments lead us to conclude that the progenitors of superintense bursts (with an energy yield larger than that for ordinary supernovae by one or two orders of magnitude) are born in massive dense star clusters, but generally flare up only after they have left the cluster; these are the same objects that are the progenitors of gamma-ray bursts (GRBs). Each of the giant stellar arcs which are grouped into multiple systems of stellar complexes in the LMC and NGC 6946 could only be produced by a single powerful energy release near its center. The progenitors of these systems of arc-shaped stellar complexes must have had a common source nearby, and it could only be a massive star cluster. Such clusters are actually known near both systems. On the other hand, calculations of the dynamical evolution of star clusters show that close binary systems of compact objects are formed in the dense central parts of the clusters and are then ejected from them during triple encounters. Mergers of the components of such systems are believed to be responsible for GRBs. Since their progenitors are ejected from the cluster before merging, the arc-shaped stellar complexes produced by GRBs are observed near (but not around) the parent clusters. If a considerable fraction of the GRB progenitors are formed as a result star encounters in massive star clusters, and if the GRBs themselves trigger star formation near the parent clusters, then observations of GRBs in star-forming regions are consistent with their origin during mergers of pairs of compact objects.     

多频带-正交频分复用超宽带系统的研究与仿真

简要阐述了多频带-正交频分复用(MB-OFDM)超宽带系统的基本原理及信号格式,具体分析了相应的发射机与接收机的基本组成与工作原理。在此基础上,利用SystemView仿真平台对发射机、接收机以及信道进行了仿真设计,并互连成一个MB-OFDM超宽带系统。最后,分别给出了功率谱密度、子频带切换以及发射端与接收端信号比较结果,通过对仿真结果的分析证明了整个系统的正确性与可靠性。     

综合河外射电源表的编制方法评述

简要介绍了编制综合外射电源表的几处方法，分析了它们各自的特点。详细讨论了ＩＥＲＳ编制方法及其系列综合表中存在的一些问题，并这些问题提出了一些改进意见。     

Automated Prediction of CMEs Using Machine Learning of CME – Flare Associations

Machine-learning algorithms are applied to explore the relation between significant flares and their associated CMEs. The NGDC flares catalogue and the SOHO/LASCO CME catalogue are processed to associate X and M-class flares with CMEs based on timing information. Automated systems are created to process and associate years of flare and CME data, which are later arranged in numerical-training vectors and fed to machine-learning algorithms to extract the embedded knowledge and provide learning rules that can be used for the automated prediction of CMEs. Properties representing the intensity, flare duration, and duration of decline and duration of growth are extracted from all the associated (A) and not-associated (NA) flares and converted to a numerical format that is suitable for machine-learning use. The machine-learning algorithms Cascade Correlation Neural Networks (CCNN) and Support Vector Machines (SVM) are used and compared in our work. The machine-learning systems predict, from the input of a flare’s properties, if the flare is likely to initiate a CME. Intensive experiments using Jack-knife techniques are carried out and the relationships between flare properties and CMEs are investigated using the results. The predictive performance of SVM and CCNN is analysed and recommendations for enhancing the performance are provided.     

类星体吸收线

类星体光谱中有大量的吸收线 ,它们或者产生于与类星体本身有联系的气体云 ,或者产生于类星体和观测者之间的吸收系统。因此 ,类星体吸收线是强有力的宇宙探针。对类星体吸收线的研究将有助于我们了解星系的形成和演化。本文介绍了类星体吸收线的性质并评述了近年来类星体吸收研究的最新进展。     

大质量恒星形成:外向流和绿色延展天体

恒星作为宇宙的基础组成元素,其形成过程一直是天文学中的重要研究对象。人们已基本了解中小质量恒星(质量小于8M⊙)的形成和演化过程;受到数量少、嵌埋深、演化快和反馈剧烈等因素的影响,大质量恒星(质量大于8M⊙)的形成过程依然谜团重重。介绍了小质量恒星形成的基本理论,以及吸积盘、竞争吸积、并合三种主流的大质量恒星形成模型;回顾了以往使用红外或射电望远镜对大质量恒星形成区的观测和分析,以及现阶段使用多波段巡天观测手段对大质量恒星形成区的研究成果;着重介绍了目前公认的大质量恒星形成的示踪物——分子外向流的理论和观测现状,以及大质量外向流的优秀候选体——绿色延展天体的发现、理论及观测研究情况。最后,对大质量恒星形成的理论和观测研究进行了总结和展望。     

Two-body relaxation in cosmological simulations

It is logically possible that early two-body relaxation in simulations of cosmological clustering influences the final structure of massive clusters. Convergence studies in which mass and spatial resolution are simultaneously increased cannot eliminate this possibility. We test the importance of two-body relaxation in cosmological simulations with simulations in which there are two species of particles. The cases of two mass ratios, √2:1 and 4:1, are investigated. Simulations are run with both a spatially fixed softening length and adaptive softening using the publicly available codes gadget and mlapm , respectively.
The effects of two-body relaxation are detected in both the density profiles of haloes and the mass function of haloes. The effects are more pronounced with a fixed softening length, but even in this case they are not so large as to suggest that results obtained with one mass species are significantly affected by two-body relaxation.
The simulations that use adaptive softening are less affected by two-body relaxation and produce slightly higher central densities in the largest haloes. They run about three times faster than the simulations that use a fixed softening length.     

CCD漂移扫描的基本原理及在天文上的应用

简要回顾了CCD在天文观测上的发展历程，介绍了CCD漂移扫描观测模式的基本原理；分析了该技术的优点和不足；综述CCD漂移扫描技术的应用现状；最后简述国内在CCD漂移扫描技术上的应用研究现状及对该技术的展望。     

Stability of the periodic solutions of the restricted three-body problem representing analytic continuations of Keplerian rectilinear periodic motions

The periodic solutions of the restricted three-body problem representing analytic continuations of Keplerian rectilinear periodic motions are well known (Kurcheeva, 1973). Here the stability of these solutions are examined by applying Poncaré's characteristic equation for periodic solutions. It is found that the isoperiodic solutions are stable and all other solutions are unstable.     

Magnetic cataclysmic variables: optical counterparts of X-ray and EUV sources

The magnetic cataclysmic variables (mCVs) are a small but astrophysically important class of X-ray source. This paper discusses some of the work carried out by the author and his collaborators on these objects, which were discovered as part of various optical identification programs of both X-ray and extreme ultraviolet sources observed by the HEAO-1 and ROSAT satellites. Definitions are given of the two classes of mCVs; the Polars and the Intermediate Polars. The reasons why mCVs are significant sources of X-ray and EUV radiation are also discussed. Individual systems which have been the subject of intensive follow-up programmes at SAAO are then described, and the implications arising from these observations are discussed.     

The equilibrium configurations of the restricted problem of 2+2 triaxial rigid bodies

The restricted 2+2 body problem is considered. The infinitesimal masses are replaced by triaxial rigid bodies and the equations of motion are derived in Lagrange form. Subsequently, the equilibrium solutions for the rotational and translational motion of the bodies are detected. These solutions are conveniently classified in groups according to the several combinations which are possible between the translational equilibria and the constant orientations of the bodies.     

Cosmological models of gamma-ray bursts

We review models of cosmological gamma-ray bursts (GRBs). The statistical and -ray transparency issues are summarized. Neutron-star and black-hole merger scenarios are described and estimates of merger rates are summarized. We review the simple fireball models for GRBs and the recent work on non-simple fireballs. Alternative cosmological models, including models where GRBs are analogs of active galactic nuclei and where they are produced by high-field, short period pulsars, are also mentioned. The value of neutrino astronomy to solve the GRB puzzle is briefly reviewed.     

库仑耦合效应对类太阳恒星模型的影响

物态方程一直是恒星模型理论研究中的最重要的物理方程之一，对于日震学等高精度要求的研究领域来讲，只包含理想效应的物态方程并不能满足研究需要，而要更细致、包含非理想效应的物态方程对系统作更精确和完善的描述，在弱耦合及弱电子简并的系统中，为研究各种带电粒子之间的库仑耦合效应，以化学图像为基础，分别用具有硬核改正的Debye—Hueckel扩展理论来处理离子-电子作用、多体作用的经典点粒子相互作用理论描述离子-离子作用和量子统计方法处理电子-电子作用，并把此3种作用对物态方程自由能的贡献用半解析的数学公式给出，为适应日震学研究的要求，特别选取一组类太阳的恒星模型作为研究对象，从实际模型计算出发，对库仑耦合中的各种效应进行了比较分析，讨论并检验了所作的理论改进。     

Quasi-periodic X-ray oscillations in the source Scorpius X-1

The RXTE observations of Scorpius X-1 in 1996–1999 are presented. The properties of its quasi-periodic X-ray oscillations are studied in detail. The results obtained are used for analysis in terms of the transition-layer model (TLM) and the relativistic-precession model (RPM) for a slowly rotating neutron star. Theoretical predictions of the two models are compared and their self-consistency is verified. The tilt of the magnetosphere to the accretion-disk plane, the neutron-star mass, and its angular momentum are determined in terms of the models.