Sternberg State Astronomical Institute Research Articles

Mass Computations of the Brightness of Stars in an Arbitrary Spectral Band

The problem of calculating the brightness of an array of stars in an arbitrary photometric band, which is not the standard band of astronomical photometry, is considered from their multicolor photometry in some other photometric system. A similar problem is to transfer photometric measurements of stars from one multicolor photometric system to another. This task includes methods for calculating and comparing magnitudes, as well as merging photometric catalogs. The questions of choice of various zero-points of photometry and reduction of measurements for the atmosphere are considered. The issues of reducing the error of the proposed methods are discussed. The article is partly based on a report presented at the conference “Modern Stellar Astronomy-2022”, held at the Caucasian Mountain Observatory of the Sternberg State Astronomical Institute, Moscow State University, in November 8–10, 2022.

Results of Astrometric Observations of Distant Satellites of Jupiter with the New Telescope of the Caucasian Mountain Observatory, Sternberg Astronomical Institute, Moscow State University

Replenishment of the database of observations of distant satellites of planets is always useful, since the accuracy of the motion models and ephemeris depends not only on the accuracy of observations. Accuracy improves with increasing observation time. Therefore, observations made even with the same accuracy are in demand. Astrometric observations of two distant satellites of Jupiter were carried out at the Caucasian Mountain Observatory (CMO) of the Sternberg State Astronomical Institute, Moscow State University, on a new telescope with a mirror diameter of 2.5 m in 2017. As a result, six positions of the J6 satellite (Himalia) and 27 positions of the J8 satellite (Pasiphae) are obtained. The root-mean-square deviations from the ephemeris for all 33 observations of these two satellites were 0.085″ in right ascension and 0.064″ in declination. This accuracy corresponds to the current level of ground-based observations. Our refinements of the orbits for the MULTI-SAT ephemeris server based on all available observations showed that the weighted root-mean-square values of the angular deviations of the measured positions from those calculated for satellites J6 (Himalia) and J8 (Pasiphae) are 0.22″ . At the same time, the accuracy of the ephemeris is estimated with the MULTI-SAT server for 2017 at 0.008″ for J6 (Himalia) and 0.05″ for J8 (Pasiphae). New observational data will be useful for refining the motion models of distant satellites of Jupiter.

An Asymptotically Optimal Algorithm for the Search for and Evaluation of the Slichter Mode from Long-Term Strain Data

The Slichter mode (1S1) is the longest-period mode of Earth’s free oscillations. The period of this mode depends on the difference between the densities of the outer liquid and inner solid cores, thus making its detection very important for the refinement of models of the Earth. Despite numerous attempts at detecting this mode with the use of a network of superconducting gravimeters, there currently is no confirmed experimental data on the observation of the Slichter mode due to its small amplitude on the surface. In this work, it is proposed to detect the Slichter mode using the data from the laser interferometer-strainmeter of the Sternberg State Astronomical Institute of the Moscow State University (Northern Caucasus) with a measuring arm length of 75 m. For this purpose, an asymptotically optimal algorithm was developed for the analysis of data with consideration for their statistical properties, and the processing of synthetic data was modeled to estimate the magnitude of the possible observed effect and the detection indicators.

Analysis of the events that occurred on July 30, 2005, according to ground-based observations in the Ca II 8498 Å line and on board spacecraft

The observations of active region (AR) NOAA 10792 in the Ca II 8498 A line with an ATB-1 solar telescope at the Sternberg State Astronomical Institute, Moscow State University (SSAI MSU) on July 30, 2005, are illustrated, and the events are analyzed using the data obtained on spacecraft. Three flares and accompanying coronal mass ejections (CMEs) are considered. It has been indicated that the beginning of the first compact CME lagged behind the flare onset by 3 min. Plasma ascended with acceleration that reached 0.4 km/s2 at the flare maximum. The matter was also apparently accelerated after the flare maximum, since an ejection could only appear at the edge of the occulting C 2 LASCO coronograph disk at 0557 UT when acceleration is about 0.5 km/s2. The second CME (of the halo type) leaded the beginning of the corresponding flare.

The Astrophysical Methods for Long-Term Monitoring of the CO<SUB>2</SUB> Content in the Earth Atmosphere

We alert the astronomers carrying high-resolution observations of the Sun to a possibility to study global changes in the composition of the Earth atmosphere and other atmospheric characteristics using spectra containing telluric lines. This possibility is illustrated by solar observations carried in Moscow in visible and near infrared spectrum. A com- parison of equivalent widths O2 (λ6295 A) and CO2 (λ20,700 A) lines, recorded with a spectrograph on the large vertical solar telescope ATB-1 at the Sternberg State Astronomical Institute from 1969 to 2007 reveals that during this period oxy- gen content in atmosphere above Moscow remained constant (within the limits of observational accuracy) whereas the carbon dioxide content increased significantly.

Astrometric results of observations at Russian observatories of mutual occultations and eclipses of Jupiter’s Galilean satellites in 2009

In 2009, in five Russian observatories photometric observations of Jupiter’s Galilean satellites during their mutual occultations and eclipses were carried out. Based on these observations, an original method was used to ascertain astrometric results such as the difference between the coordinates of pairs of satellites. Fifty-three phenomena were successfully observed. A total of 94 light curves of satellites were measured. The error in the coordinates of satellites due to random errors in photometry, calculated on all data obtained, was 0.041″ in right ascension and 0.046″ in declination. The discrepancies between the theory and observations in these coordinates was found to be 0.060″ and 0.057″, respectively. The results were uploaded to the common database for all observations of natural satellites of planets at the Natural Satellites Data Center (NSDC), which is available online at http://www.sai.msu.ru/neb/nss/index.htm. For the first time in the practice of photometric observations of satellites in epochs of mutual occultations and eclipses a new method of observation was tested, which eliminates from astrometric results the major systematic errors caused by an inaccurate account of the background level. The tests were conducted in the Terskol Observatory and the observatory of the Crimean laboratory of the Sternberg State Astronomical Institute of the Moscow State University. The application of the new method showed that the elimination of the background level at these observatories was carried out correctly.

On ejection of solar plasma enriched with 3He and Fe I at boundaries of coronal holes

The spectra and spectroheliograms in the He I λ = 1083.03 nm IR-line obtained with the horizontal solar telescope of the Sternberg State Astronomical Institute (SSAI) of Moscow State University are analyzed for the purpose of studying the increased solar activity at the boundaries of coronal holes. Our observations demonstrate plasma flux intensification at the boundary separating a coronal hole and a bipolar active region. In this case, the spectra in the vicinity of the He I λ = 1083.03 nm line point to a significant intensification in the lines of light isotope 3He I λ = 1083.168 nm and Fe I λ = 1082.837 nm. Acceleration of solar plasma fluxes at the coronal hole boundary in the immediate vicinity of an active region seems to be the result of reconnection of bipolar structure magnetic fields in the active region and a unipolar field of the coronal hole. The nature of 3He and Fe I particle enrichment in upward fluxes at the coronal hole boundaries is discussed.

A Laser Interferometer-Deformograph for Monitoring the Crust Movement

A laser interferometer-deformograph with a 75-m-long arm has been developed by Moscow State University's Sternberg State Astronomical Institute to record and study lithospheric deformations over a wide frequency range. The design and the performance characteristics of the interferometer are described. It is located near Mount Elbrus, in one of the Russian regions with the highest level of geodynamical activity, which determines the range of geophysical and geodynamical problems to be solved using experimental data obtained with this instrument. Based on experience gained over ten years of routine observations, the whole measuring system has been comprehensively updated. As a result, its technical potentials have been substantially extended and the reliability and quality of experimental data have been improved. The limiting sensitivity of the laser interferometer is assessed, and the results from observations are presented.

SPECTROPHOTOMETRIC OBSERVATIONS OF M, S AND E ASTEROIDS AT THE STERNBERG ASTRONOMICAL INSTITUTE AND THE CRIMEAN ASTROPHYSICAL OBSERVATORY

Investigation of M, S and E asteroids are important for the problem of the evolution of the Solar System. Observations have been carried out by means of a joint programme using telescopes of the South Station of the Sternberg State Astronomical Institute, the MTM-500 telescope of the Crimean Astrophysical Observatory and telescopes of other observatories. Up to 400 spectra of five asteroids (3 Juno, 21 Lutetia, 55 Pandora, 88 Thisbe and 393 Lampetia of S, M, M, CF and C types respectively) have been obtained at the Crimean Astrophysical Observatory during autumn 2000. Instances of observed spectra are presented.

Photometric classification of poorly known variables S 8348=NSV 12742, S 8351=HT VUL and S 8352=NSV 12763

Abstract The stars were studied on negatives of the Sternberg State Astronomical Institute and the Abastumani Astrophysical Observatory. The stars are classified as EB (NSV 12742, P = 0d.4662417), SX Phe (HT VUL, P = 0d.12677192) and EA (NSV 12763, P = 1d.735215).

A large-scale puzzle

A large-scale puzzle

The Photometric (UBV) Study of the Planetary Nebulae Variability in 1968–1987

The photoelectric UBV-observations of planetary nebulae variability, begun in 1968 at Crimean Station of Sternberg State Astronomical Institute (USSR) and Skalnate Pleso Observatory (Czechoslovakia), were carried out during 20 years, 1987 inclusive.

Joint Spectrophotometric Catalogue of the Sternberg State Astronomical Institute and Fessenkov Astrophysical Institute: The analysis of common stars

TheSpectrophotometric Catalogue of the Sternberg State Astronomical Institute contains 875 stars; 8 of them are standards. TheCatalogue of the Fessenkov Astrophysical Institute consists of 1123 stars. The data on the spectral energy distribution for about a half of these stars are published. A comparison of energy distribution data for 473 common stars in the range 3200–7600 A was made. Calibration of Alpha Lyr from Hayes (1985) was used for all the stars of both catalogues. In difference of the previous publications the comparison includes much more stars and energy distribution data were corrected where necessary. The agreement between the corrected data is better than in the case of the earlier comparison. Reductional factors due to the instrumental effects were taken into account for 275 stars from theSternberg Institute Catalogue. These factors are in the limits 1.01–1.04 and their mean value is 1.03. The reductional factors for the stars from theFessenkov Institute Catalague are much larger: 1.06–1.12 with the mean 1.06–1.07. In this case the reduction factors were taken into account for all the stars of the catalogue except the brightest ones withV<2.0. The values of the differences between spectral energy distribution data for common stars in dependence of magnitude, spectral type, and wavelength are presented.

The Absolute Spectrophotometry of 170 Planetary Nebulae

An investigation of planetary nebulae has been underway at the Sternberg State Astronomical Institute in Moscow for several years. It was begun with the measurement of the emission-line intensities of planetary nebulae in an homogeneous system in absolute units. More than 300 long-exposure objective prism spectrograms were obtained with the 50-cm Maksutov telescope at the Crimean Station of the Institute and with the 70-cm meniscus telescope of the Abastumani Observatory. The dispersion of the spectrograms was 190 and 160 Å/mm at Hγ respectively.

Observations of Planetary-Nebula Spectra in the Near Ultraviolet

Several dozen spectrograms of about 20 nebulae were obtained with the quartz spectrograph, placed at the Cassegrain focus of the 125-cm parabolic reflector of the Sternberg State Astronomical Institute Crimean Station. Nebulae with intense Balmer continuum were selected. Nearly half of them had not been studied before. Reductions were made for the nuclei spectra, for the differential atmospheric extinction and for the interstellar absorption. The A0 V stars were taken as absolute intensity standards. The work is not yet finished, but the results will be received in a short time.

Some conclusions on the structure of Antarctica

Abstract This paper describes the gravimetric investigations of the Sternberg State Astronomical Institute in Antarctica. On the basis of data from gravimetry and other geophysical methods, it has been possible to construct a picture of the rock basement of Antarctica, the nature of the gravitational field, and the thickness of the Earth's crust and isostatic equilibrium in that area. The important features of the structure of East and West Antarctica are noted. The former possesses the characteristic features of a stable continent, whereas the latter constitutes an intermediate stage between a continent and a group of islands.