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Using Balmer Line Shapes to Diagnose Physical Conditions in Collisionless Shock Waves
Hartigan, Patrick; Raymond, John C.; Ghavamian, Parviz
When a collisionless shock propagates through a partially ionized, tenuous medium (n<=1 cm-3), the neutral atoms overrun by the shock produce Balmer line emission as they are excited by collisions in the hot postshock gas. The collisional excitation of neutral atoms and their charge exchange with hot postshock protons produces both n…
Starspot Model of RS CVn Type Binary SZ PSC
Kang, Young-Woon
The emission lines of the ultraviolet region and the light curves of the optical region have been analyzed to investigate the distorted light curves of SZ Psc. The Mg II emission lines of the IUE spectra confirmed that the chromospheric activity of SZ Psc occurs on the K1 IV star. The distorted light curves in the optical region have been analyzed…
Is the small-amplitude cepheid SZ Tau a possible overtone pulsator?
Andrievsky, S. M.; Kovtyukh, V. V.; Klochkova, V. G. +3 more
On the base of 8 high-resolution CCD spectra, obtained by the 6-m telescope of SAO RAS (Russia) and 4-m telescope of KPNO (USA), we have determined the mean values of atmospheric parameters for small-amplitude Cepheid SZ Tau. Since SZ Tau is a member of NGC 1647 open cluster and calibrating object for ``period - luminosity" relation, it is very im…
Crossing a comet's tail.
Jones, G. H.
The Ulysses spacecraft returned some very strange readings which are now identified.
Positional and photometric supplement to the compiled GPM catalogue of proper motions of stars referred to galaxies
Rybka, S. P.
Precise positions and three-color B, V, R photometric data selected from all available sources were included into the GPM catalogue. The Tycho, GSC, and USNO-A2 catalogues are the main sources. The data were investigated for systematic and random errors and reduced to a uniform system.
Recalculated Orbits of 8 Double Stars
Olevic, D.; Jovanovic, P.; Popovic, G.
The authors present new orbital elements for the following pairs: ADS 1227 ADS 3317, ADS 8128, ADS 8239, ADS 8242, ADS 8539, ADS 8949 and McA 61. Individual masses for these pairs are also calculated. For the pairs ADS 8128, ADS 8239, ADS 8539 and ADS 8949 calculated parallaxes are in accordance with the corresponding parallaxes of the Hipparchos …
Short-Period Variations in the Proper Motions of Sunspots from SOHO (MDI) Observations
Didkovskiĭ, L. V.
Short-period (1 60 min) variations in the coordinates of the centers of gravity of isolated sunspots are analyzed. The sunspot coordinated were determined using two sets of observational data—magnetograms and intensities—obtained by SOHO (MDI) on December 6, 1998, from 01:00 to 21:57 UT with temporal resolution 60 s and spatial resolution 0.6″/pix…
The proper and space motions of the globular cluster NGC 4147 on the Hipparcos system
Wang, Jia-ji; Wu, Zhen-yu
Dr M. Geffert, of Sternwarte der Universität Bonn, kindly provided us with the positions and proper motions of 82 stars in the field of the globular cluster NGC 4147, reduced with 11 reference stars from the Hipparcos catalogue. We used 54 of these stars to re-reduce the observations by Wang Jia-ji and Gupta [1]. Based on the new proper…
Proper motions of Hipparcos stars in two plate areas
Wang, Shu-he; Tang, Zheng-hong; Jin, Wen-jing
Using the ACT reference catalogue as preliminary reference we have reduced 31 exposures on 15 plates in two areas taken with the 40-cm refractor of our Observatory. Using the central overlapping technique and an iterative procedure we have derived high-precision positions and proper motions for 54 stars, including 16 Hipparcos stars. For the latte…
Contributions of the Bucharest Observatory to the CONFOR program
Bocsa, Gheorghe
The connection between the optical reference frame and the radio one constitutes one of the main purposes of the astrometry. The paper is pointing out the contribution of the Bucharest Observatory in this direction. The statistic analysis of the standard errors for the astrometric PPM and TYCHO stars is presented.