Search Publications
Proper Motions of Open Star Clusters and the Rotation Rate of the Galaxy
Beshenov, G. V.; Loktin, A. V.
The mean proper motions of 167 Galactic open clusters with radial-velocity measurements are computed from the data of the Tycho-2 catalog using kinematic and photometric cluster membership criteria. The resulting catalog is compared to the results of other studies. The new proper motions are used to infer the Galactic rotation rate at the solar ci…
Large-scale Dimmings Produced by Solar Coronal Mass Ejections According to SOHO/EIT Data in Four EUV Lines
Grechnev, V. V.; Chertok, I. M.
SOHO/EIT data are used to analyze dimmings, or transient coronal holes (regions of reduced soft-X-ray and EUV emission), which are observed on the solar disk after halo-type coronal mass ejections (CMEs). Simultaneous observations in the 171 Å FeIX/X, 195 Å FeXII, and 284 Å FeIX coronal lines, which are sensitive to temperatures of T e ≈1.2, 1.5, …
The Subsystem of Open Clusters in the Post-Hipparcos Era: Cluster Structural Parameters and Proper Motions
Piskunov, A. E.; Kharchenko, N. V.; Pakulyak, L. K.
The wide neighborhoods of 401 open clusters are analyzed using the modern, high-precision, homogeneous ASCC-2.5 all-sky catalog. More than 28000 possible cluster members (including about 12500 most probable members) are identified using kinematic and photometric criteria. Star counts with the ASCC-2.5 and USNO-A2.0 catalogs are used to determine t…
Solar Large-Scale Channeled Dimmings Produced by Coronal Mass Ejections
Grechnev, V. V.; Chertok, I. M.
A new type of dimmings, or transient coronal holes (i.e., regions of reduced soft-X-ray and EUV emission), is revealed in analyses of difference solar images obtained with the SOHO EIT ultraviolet telescope at 195 Å. Such features can be observed on the solar disk after halo-type coronal mass ejections (CMEs). If several active regions, filaments,…
Identifying Compact Moving Groups Based on Stellar Kinematics Data
Flynn, C.; Orlov, V. V.; Myullyari, A. A.
We investigate the possibility of identifying substructures in velocity space in three well-known stellar streams (the Hyades, the Pleiades, and Ursa Major) using a cluster-analysis method (the maximum-density method). Only compact groups in velocity space with radii no greater than 5 km/s and containing at least 10 members were considered. As an …
The Structure of Proper-Motion Diagrams for Nearby Stars
Vereshchagin, S. V.; Reva, V. G.; Chupina, N. V.
The structure of the proper-motion diagrams for an ensemble of nearby field stars is analyzed using a simple model. For comparison, the observed proper-motion diagram is constructed using data of the Hipparcos catalog. A complete description is given of the modification of the van Altena method, which allows stars with similar space motions to be …