Variation of the Flare Frequency of Flare Stars. II. Flare Stars of the Pleiades Cluster

The possible variation of the flare frequencies of flare stars in the Pleiades cluster is considered. It is shown that of the 75 chosen stars that each exhibit five or more flares, 33 can be suspected of variation of flare frequency at the 0.1 significance level.     

Possible Flare of the Red Dwarf HU Del

The results of spectroscopic observations of the red dwarf flare star HU Del are given. The observations were made in August 2000 with the 2.6-m telescope of the Byurakan Observatory equipped with a Byu FOSC integral-field spectrograph. A rapid flare evidently occurred on HU Del.     

重新审查昴星团成员星锂丰度的弥散

重新审查了昴星团成员星的活动性和在同一颜色处Li丰度的弥散．发现大多数的研究者低估了昴星团恒星的活动性．重新研究了恒星的活动性(包括黑子活动)和星团中恒星的不均匀红化效应对Li丰度弥散的影响．得到的主要结论是：没有坚实的证据说明观测到的Li丰度弥散是代表具相同有效温度星团成员大气Li丰度存在真实的差异．相反，假若不是全部，其大部的视Li丰度弥散是活动星的大气效应所致．Li丰度一恒星自转关联很可能只是Li丰度-恒星活动性关联的一种反映。     

Spectral Observations of the Flare Star HU Del

Results are presented from a study of 27 spectra of the flare star HU Del obtained during 2000–2002 on the 2.6 meter telescope at the Byurakan Observatory. Two flares were detected, along with a weak correlation between the equivalent widths of the Hα and Hβ emission lines. At the time of the photometric maximum of a flare the equivalent widths of both these lines are minimal and reach their maximum only significantly afterward. A strong increase in the Hβ line intensity is observed which appears to be the consequence of a photometrically undetected, short-duration flare. A possible relationship between the binary (multiple) character and the physical activity of this star is examined briefly in terms of current theoretical models.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 335–348 (August 2005).     

Velocity Distribution of Stars in the Pup-CMa Association

The distribution of proper motions of stars in the Pup-CMa association is presented. The stars' velocities are approximately parallel to each other, which indicates that the stars are close together in space. The mutual distribution of stars and molecular clouds in the association is interpreted as proof that the stars emerged from a single gigantic primordial molecular cloud (or several large clouds), destroyed by radiation and/or stellar wind coming from those stars. It is assumed that part of that cloud is being dissipated, while part is being broken into several small clouds, which we are observing at present.     

Flare variability in the close binary FL Vir

The results of U -filter flare monitoring of the binary flare star FL Vir = Wolf 424 is presented. 57 flares with energies between  2 × 10²⁸  and  2 × 10³¹ erg  were recorded in 20 h of observation. The properties of flare occurrence and flare time-scales are analysed, and the flare activity level in 1980 April is determined to be   L _f( U ) = 8.0 × 10²⁶ erg s⁻¹  . This is larger than previously published results and may indicate a variation in the flare activity level on a time-scale of years. An analysis of existing data indicates that the flare activity level correlates with the relative orbital positions of the stars.     

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.     

A new flare star member candidate in the Pleiades cluster

We present a new flare star, which was discovered during our survey on a selected field at the edge of the Pleiades cluster. The field was observed in the period 2007–2010 with three different CCD‐cameras at the University Observatory Jena with telescopes from 25 to 90 cm. The flare duration is almost one hour with an amplitude in the R‐band of about 1.08 mag. The location of the flare star in a color‐magnitude diagram is consistent with age and distance of the Pleiades. In the optical PSF of the flare star there are two 2MASS objects (unresolved in most images in the optical Jena PSF), so it is not yet known which one of them is responsible for this flare. The BVRIJHK colors yield spectral types of M1 and M2 with extinction being A_v = 0.231 ± 0.024 mag and A_v = 0.266 ± 0.020 for those two stars, consistent with the Pleiades cluster (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spatial Distribution of Magnetic CP Stars

The spatial distribution of magnetic CP stars is studied using the catalog of CP stars compiled by the Special Astrophysical Observatory of the Russian Academy of Sciences. It is shown that the overwhelming majority of these objects are at distances closer than 500 pc from the sun. The axes of rotation and the magnetic axes of the field CP stars are distributed randomly, while a preferential orientation of the magnetic axes in certain directions is seen for stars that are members of open clusters. The closeness of the magnetic models for CP stars that are members of clusters may be evidence that there is a general factor which influences the origin of magnetic fields in stars. The magnetic field of the galaxy may be such a factor.     

Variation in the Flare Frequency of Flare Stars. III. Flare Stars in the Orion Association

The possible variation of the flare frequency of flare stars in the Orion association is considered. It is shown that of the 23 chosen stars, each having exhibited four or more flares, a change in flare frequency at the 0.1 significance level can be suspected for 13.     

The Spatial Distribution of W UMa-Type Stars

The aim of this project is to study the spatial distribution of contact binaries and to compare the sample from the project of study the W UMa-type stars, with existing databases such as Hipparcos, GCVS or ASAS (ESA, 1997; GCVS, 2005; Pojmanski, 2002).     

Frequency Distribution Function of Stellar Flares for Faint Stars in the Pleiades Cluster

It is shown that to derive the distribution function of the average frequency of stellar flares in a case in which the number of flares observed in an aggregatation is small, a chronology of third flares can be used to confirm the chronology of first flares. A concrete solution for faint stars of the Pleiades cluster is given.     

恒星射电耀发6cm波段偏振观测试验

利用新疆天文台南山基地25m射电望远镜在6cm波段对恒星V772 Her和βPer进行了偏振观测试验.通过数据处理和校准得到恒星的射电光变曲线.探测到V772 Her的射电耀发现象,耀发时的线偏振度约达30%,偏振位置角约4°;探测到βPer的缓变成份及叠加其上的快速耀发,βPer耀发时线偏振很弱.     

太阳6659号活动区的白光耀斑

1991年6月6日我们在太阳6659号活动区观测到了一个白光耀斑.这个白光耀斑伴有强烈的H_α、X射线和射电微波发射.我们对这次自光事件作了初步的分析研究,并对它的总能量作了粗略估计.