Search Publications
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 …
Intermediate-Brightness Equatorial Spectrophotometric Standards
Tereshchenko, V. M.
We have obtained spectral energy distributions for 41 7m 8m stars near the celestial equator (δ=±3°). The λλ3100 7600 Å spectral range is studied with a spectral resolution of 50 Å. The relative rms error in the visible is 1 2%, increasing to 3 5% towards the edges of the wavelength interval studied. All stars are referenced to a single standard, …
Revised Magnesium Abundances in Galactic Halo and Disk Stars
Mashonkina, L. I.; Shimanskaya, N. N.
A differential analysis of the magnesium abundances in 61 F-K dwarfs and subgiants with metallicities -2.6<[Fe/H]<+0.2 is performed based on published observational data. Fundamental parameters for 36 stars are determined: T eff from V-K and V-R; logg from HIPPARCOS parallaxes, and [Fe/H] and ξt from Fe II lines. The computations allow for n…
Luminosity calibration for OB stars from Hipparcos trigonometric parallaxes
Beshenov, G. V.; Loktin, A. V.
Hipparcos trigonometric parallaxes and observational data for open clusters are used to determine the absolute magnitudes MV of O and B stars of various spectral subtypes and luminosity classes, including those with broadened lines and hydrogen emission lines. The same data are used to derive a relation between MV and the ind…
Intermediate-Brightness Spectrophotometric Standards. Standards Near +40° Declination
Tereshchenko, V. M.
The second stage in our program to compile a list of regional intermediate-brightness spectrophotometric standards has been completed. We have obtained spectral energy distributions for 24 stars with magnitudes near +40° declination. The range λλ3100 7600 Å was studied with a spectral resolution of 50 Å. The relative rms error of our results in th…
Intercombinational Line Profiles in the UV Spectra of T Tauri Stars and Analysis of the Accretion Zone
Lamzin, S. A.
We have analyzed for the first time profiles of the SiIII 1892 Å and CIII 1909 Å intercombinational lines in HST spectra of the stars RY Tau and RU Lup. The widths of these optically thin lines exceeded 400 km/s, ruling out formation in the stellar chromosphere. Since the intensity of the Si line exceeds that of the C line, it is unlikely that a l…