BD＋47819：一颗A5型特殊耀星

本作在对αＰｅｒ疏散星团的观测工作中发现了一颗罕见的早型亮耀星。从对其光谱观测的结果，可以确定它为－Ａ５型星，这与传统恒星耀发理论是相悖的。     

BD＋47819：一颗A5型特殊耀星

本文作者在对αＰｅｒ疏散星团的观测工作中发现了一颗罕见的早型亮耀星，从对其光谱观测的结果，可以确定它为－Ａ５型星．这与传统恒星耀发理论是相悖的。     

大质量年轻星团和超星团

随着观测技术的进展,在星系中观测到了越来越多的大质量年轻星团和超星团,它们不能简单地归类于银河系中的疏散星团或球状星团,因而其性质和演化意义日益为人们所关注。该文对大质量年轻星团和超星团的发现、观测特征以及演化意义进行了较为系统的概要介绍。     

OB星协和年轻星团的形成与早期演化

ＯＢ星协和年轻星团是恒星形成与早期演化的“化石”，同时也是研究初始重质量函数（ＩＭＦ）的最好场所；文中就ＯＢ星协和年轻星团的形成和早期演化方面的研究进展作了一评述，还论述了ＩＭＦ的测定和研究情况，并对相关的速逃ＯＢ星及蓝离散星问题作了简要介绍。     

老年疏散星团的金属丰度及银盘金属丰度梯度演化研究

疏散星团是探究银河系结构与演化的良好示踪体,一直以来颇受关注.之前关于疏散星团的研究中,仅有一小部分疏散星团有金属丰度参数,而且,金属丰度的测量,是基于不同质量的观测数据,采用了不同的方法.收集了一个年龄大于2 Gyr的老年疏散星团样本,通过整理这些星团成员星的金属丰度数据,一方面,以星团NGC 2682为例,对比了不同光谱巡天项目给出的星团成员星金属丰度的系统差异;另一方面,计算了星团成员星金属丰度的平均值和中位值,作为该疏散星团的金属丰度推荐值.此外,还利用该样本探究了银盘径向金属丰度梯度随时间的演化,结果表明,早期银盘有着更加陡峭的径向金属丰度梯度,随着演化时间的增加,银盘径向金属丰度梯度逐渐趋于平缓,为银盘化学演化模型提供了更加严格的观测约束.     

昴星园天区耀星成员性和相对数量的再讨论

本文通过统计比较，并用更完善的模型作成员概率的最大似然估计，对昴星园天区耀星的成员性进行了新的细致的讨论，指出Ｍｉｒｚｏｙａｎ等根据Ｊｏｎｅｓ的自行成员概率估计得出的非成员耀星呈现团心集中强烈趋势的现象，是由于Ｊｏｎｅｓ对成员概率的普遍低估以及对外围恒星成员概率的一定程度高估加上在中心附近观测误差和错误显著增加而造成的。     

星团成员辨认方法研究进展

对疏散星团进行成员星辨认是研究疏散星团的性质和确定疏散星团基本属性参数的首要步骤,对利用疏散星团开展的恒星演化以及银河系结构等研究方向具有重要意义。利用恒星运动学方面的信息(自行和视向速度)来建立可靠的成员星辨认模型,是成员星辨认领域中一个重要的研究方向。目前利用运动学数据进行成员星辨认较为成熟的模型主要是Vasilevskis-Sanders的方法和非参数方法。除此之外,还有一些新兴的方法:建立多维模型和聚类算法等,但这些方法还有待于进一步探索。随着天体测量技术的不断发展,测量数据精度不断提高,提高成员星辨认模型可靠性的需求也越来越迫切。综述了用运动学方法对星团进行成员星辨认的研究背景和研究现状,对各类算法进行了简要介绍,总结了每种模型的优缺点。最后,在Gaia时代下,对成员星辨认模型的研究发展进行了展望。     

银盘的径向金融丰度梯度

详细综棕了银盘（包括HII区，早B型星，行星状星云和疏散星团）径向元素丰度梯度的观测结果，分析了丰度梯度的空间和时间变化的情况，指出根据目前的观测结果，还很难确定在银盘的演化历史中径向元素丰度梯度是逐渐变平缓还是逐渐变陡，比较了目前各种化学演化模型对径向丰度梯度演化的预测结果，初步探讨了丰度梯度可能的产生机制及影响其演化的各种重要物理过程。     

年轻星体的近红外观测与研究

本对３６颗不同质量、不同演化阶段的年轻星体进行了Ｊ，Ｈ，Ｋ波段测光，并结合其它光学、近红外、ＩＲＡＳ、亚毫米、毫米波段的观测结果，计算了它们的红外色指数、能谱分布指数、红外光度等参量，得到近红外和远红外双色图，比较了不同类别源的参量分布。最后，在前人工作的基础上，改进了低质量主序前星的辐射模型，对一些源进行了计算并分析其星周状况。     

年轻星体的近红外观测与研究

本文对36颗不同质量、不同演化阶段的年轻星体进行了J，H，K波段测光，并结合其它光学、近红外、IRAS、亚毫米、毫米波段的观测结果，计算了它们的红外色指数、能谱分布指数、红外光度等参量，得到近红外和远红外双色图，比较了不同类别源的参量分布．最后，在前人工作的基础上，改进了低质量主序前星的辐射模型，对一些源进行了计算并分析其星周状况．     

疏散星团的质量分层

对疏散星团质量分层的有关问题做了简要的评述,包括空间质量分层和速度质量分层的表现形式和探测途径,质量分层形成机制的研究现状.最后概要介绍了2MASS测光资料对探讨疏散星团质量分层效应的作用.     

Flare star activity in the open cluster Alpha Persei

The results from a flare star investigation in the open cluster Alpha Persei are presented. Photographic flare star monitoring and CCD photometry of the discovered 4 new flare stars are made. The flare star activity phenomenon is restricted to the classical flare stars (UV Ceti type) as classified in the GCVS. The V/V‐I diagramme of the members of the cluster with the locations of the considered flare stars is given. Most of the flare stars are probable cluster members. The flare frequency determined from the Rozhen flare star monitoring is very low–one flare event occurs for 38.5 hours effective observing time. Comparison with the flare activity of the Pleiades is made because of the small difference in the age and distance of the clusters.     

Spectral observations of red dwarfs II. New observations of flare stars in the Pleiades cluster region

We studied the spectra of 24 flare stars of the Pleiades cluster region obtained on the 2.6m telescope of the Byurakan observatory in the years 1986–1989. From the spectral indices of titanium oxide (TiO) and other chemical elements of the stars investigated we determined their spectral classes and luminosities (absolute visual stellar magnitudes). The agreement of these moduli of the stars with the distance modulus of the Pleiades cluster confirms that 21 of them belong to the cluster. Only three of them (FSP 169, FSP 377, and FSP 435) are possibly not members of the cluster. This indicates that the flare activity of a star is a reliable criterion for its membership in a nearby stellar system (cluster or association).Translated fromAstrofizika, Vol. 37, No. 4, 1994.     

Numerical simulations of the Hyades dynamics and the nature of the moving Hyades cluster

We present our numerical simulations of the dynamical evolution of the Hyades open cluster. The simulations were performed usinga modified NBODY6 algorithm that included tidal forces and a realistic orbit of the cluster in a gravitational field described by the Miyamoto-Nagai potential. Our goal was to study the nature of movingclu sters. We show that the stars that were earlier cluster members could be later identified within a sphere of 50 pc in diameter around the Sun. The number of such stars for the chosen initial mass and virial radius of the cluster does not exceed ten. The maximum space velocity of these stars relative to the core of the current cluster does not exceed 3 km s^?1. Our numerical simulations confirm the assumption that some of the moving clusters near the Sun could consist of stars that have escaped from open clusters in the course of their dynamical evolution.     

On the 100-th anniversary of the birth of Academician V. A. Ambartsumian

A brief review is given of the applications of some methods, mainly developed at the Byurakan Observatory, to the statistics of flare stars. These developments originate in papers by Ambartsumian which led to the fundamental conclusion that a stage of flare activity is a natural stage in the evolution of red dwarf stars. In terms of their scientific value and novelty, the mathematical methods developed by Ambartsumian for solving specific astrophysical problems in the statistics of flare stars are just as significant as the astrophysical results obtained using these methods.     

Frequency Distribution of Bursts from Randomly Flashing Objects Determined by the Method of Moments

A new method is proposed for determining the frequency distribution of bursts from randomly flashing objects based on fitting Pearson distributions by the method of moments. This method is applied to flare stars in the Pleiades cluster and the Orion association. The desired frequency distribution of the bursts from flare stars can be approximated by a gamma distribution. The burst frequency distribution describes the observed statistical picture fairly well. The result is compared with other methods.     

疏散星团M11的研究:3.团星分布的两点相关函数分析

本文首次利用两点相关函数，对著名中年疏散星团M11团星的空间分布进行了讨论．结果表明，无论对全部成员星还是不同星等的成员星，它们的自相关和交叉相关函数都能很好地以幂律形式描述．不同星等成员星的自相关和交叉相关计算表明，M11已经历了一定的动力学弛豫，出现了质量的空间分层效应．     

年轻疏散星团NGC 2244的成员概率与空间运动

利用绝对自行资料,确定了年轻疏散星团NGC 2244天区恒星的运动学成员概率,并对星团成员概率以及自行矢量的分布、不同成员概率恒星的位置分布情况、径向数密度轮廓等进行了讨论并给出了星团的特征尺度;进一步结合已知的星团距离和视向速度资料,计算了NGC 2244的三维空间运动速度,结果表明NGC 2244是一个典型的薄盘族星团。     

Activity and kinematics of members of the TW Hydrae association

We present high-resolution echelle spectroscopy of 20 stars in 16 systems catalogued as members of the TW Hydrae association, and 16 stars identified as possible new members. We have calibrated the range of coronal and chromospheric activity expected for such young stars as a function of spectral type by combining our observations with literature data for field and open cluster stars. We also compute space motions for TWA members and candidate members with proper motion measurements, using two techniques to estimate distances to stars lacking direct trigonometric parallax measurements. The mean space motion of the four TWA members with known parallaxes is  ( U , V , W : −10.0, −17.8, −4.6) km s⁻¹  . 14 of the candidates have properties inconsistent with cluster membership; the remaining two are potential new members, although further observations are required to confirm this possibility.     

Subsystems of flare stars of different ages in Orion and the Pleiades

The two best-studied subsystems of flare stars, in Orion and the Pleiades, which are of considerably different ages, are compared. It is shown that the observed differences between them are consistent with the evolutionary status of flare stars that represent a stage in the evolution of red dwarfs. It is found that less luminous stars exhibit higher flare frequencies. For equally luminous stars, flare activity is lower in older stars.Translated from Astrofizika, Vol. 37, No. 1, pp. 59–72, January–February, 1994.