K. V. Kuimov

Physical origins for variations in the apparent positions of quasars

The physical origins of the apparent motion of radio sources in the ICRF are considered. The sources can be divided into four groups, according to the characteristics of their motion. Here, we consider the model for the motion of the first group of sources—those displaying uniform linear motion. Since the apparent speeds of the radio sources are close to, and sometimes exceeding, the speed of light, it is natural to suppose that these sources are relativistic jets or plasma clouds moving with speeds close to the speed of light. Uniform linear motion can be explained by a model invoking precession of the jet. We consider the physical characteristics of a number of selected sources of the ICRF in the proposed model.

The celestial reference frame stability and apparent motions of the radio sources

Time series of the coordinates of the ICRF radio sources were analyzed. It was shown that part of radio sources, including even the so-called “defining” sources, show a the significant apparent motion. Corrections for their a priori coordinates are time functions. The celestial reference frame stability is provided by the no-net-rotation condition applied to the selected subset of sources, which leads in our case to a rotation of the frame axes with time. Parameters of this rotation were calculated for different subsets of sources. To improve stability of the celestial reference frame new methods of selection of the extragalactic radio sources were suggested. The first one was called “cosmological” and the second one “kinematical”. It was shown that a selected subset of the ICRF sources, according to cosmological criteria, determines the most stable coordinate system during next decade.

An annular eclipse on May 31, 2003, observed in extreme ultraviolet

The CORONAS-F spacecraft crossed the zone of the ring solar eclipse three times on May 31, 2003. A considerable decrease in solar radiation was detected by the spacecraft instruments for these moments. The passages through the eclipse zone were registered by the VUSS instrument, which measured the shortwave solar radiation flux near the hydrogen Lyman alpha line, and by the DIFOS instrument, which was sensitive to infrared, visible, and near-ultraviolet radiation. The eclipse is also clearly seen in solar images obtained by the X-ray SPIRIT telescope. Some details of measurement results are discussed.

Precision astrometry with schmidt telescopes

Schmidt telescopes currently provide nearly the only means to obtain positions of faint objects with respect to the standard ICRS reference system. However, the lack of adequate astrometric calibration methods to account for the specific properties of Schmidt telescopes leads to residual systematic errors of up to 1″. The main source of systematic errors is plate bending during exposure. A high-precision reduction technique to account for this effect is proposed. Application of this technique to observations acquired with the Schmidt telescopes of the Palomar and Anglo-Australian Observatories reduced the systematic errors by a factor of 2.5 and gave them a simpler structure, while simultaneously decreasing the number of unknowns in the reduction model threefold. Application of the new method, with appropriate account for the design of the particular plateholder used, will make it possible to use Schmidt telescopes to determine high-precision positions for virtually all objects detected in photographic surveys.

A multipole analysis of the apparent motion of reference radio sources

In this paper, the apparent motions of quasars, which are the reference sources of the international celestial reference system (ICRS), are analyzed. Kinematic parameters from four catalogs compiled by different research groups are used. Apparent motions are expanded on a special set of vector functions on the sphere that are an irreducible representation of the rotation group O(3). The degree of the noninertiality of the barycentric reference system caused by the rotation of the solar system around the galactic center is estimated according to expansion coefficients. The direction and magnitude of the acceleration vector are calculated and compared with the alternative estimates. This method is discussed as a way to test Newton’s law on a large scale.

Results of the new reduction of positional observations of the asteroid Ceres

The results of a new reduction of positional observations of the asteroid Ceres are presented. The observational material was obtained in the State Astronomical Institute using the wide-angle astrograph AFR-1. The interval of photographic observations is 30 years, from August 1956 to May 1986. Measurements of the relative coordinates of stars and the asteroid were submitted electronically. A new model of reduction and a modern catalogue of stellar positions, the reference catalogue Tycho, were used in the calculations. Right ascension and declination of the asteroid at the time of observations were obtained from the International Celestial Reference Frame. The estimate of the mean square error of one measurement is 0.25″.

Principles for selecting a list of reference radio sources for a celestial coordinate system

Time series of the coordinates of radio sources defining the celestial coordinate frame are analyzed. Methods for selecting such sources so as to enhance the stability of the frame are considered. Some of these sources, including so-called “defining” sources, demonstrate significant proper motions. Since the stability of the celestial coordinate frame is determined by an absence of global rotation relative to the defining sources (no net rotation), variation in their coordinates will lead to a rotation of the axes of the celestial coordinate frame. The parameters of this rotation are calculated for two physical models for the motions of extragalactic radio sources. The motions displayed by the first group of sources are linear and uniform. Since the apparent speeds of radio sources are often close to, and sometimes exceed, the speed of light, it is supposed that such radio sources have relativistic jets or plasma clouds that move with speeds roughly equal to the speed of light. The observed uniform, linear motion can then be explained by precession of the jet. The second group of sources display non-linear motions, interpreted as a manifestation of the acceleration of matter by the jet. It is assumed that a cloud of particles that moves into the path of the jet is accelerated to relativistic speeds by the jet. A list of sources that should form a very stable coordinate system for several decades into the future is composed based on these two models.

Completion of the Sternberg Astronomical Institute Astrographic Catalogue Project

The first astronomical photographic survey, the Carte du Ciel was initiated in 1887 by a group of French astronomers. The observational campaign was started in 1891, while the last of more than 22,000 total plates were photographed in 1950; most of observations (more than 90%) were performed prior to 1920. Detailed description of the Carte du Ciel development can be found elsewhere (Kolchinsky 1989, Eichhorn 1974, Debarbat et al. 1987).