Astrophysical Bulletin最新文献

A local integral that allows us to immediately determine the velocity field for certain specific initial conditions was introduced by Antonov and Shamshiev in 1992. We consider cases where the integrability of the trajectory can be advanced further. We then obtain an analytical relationship between (x), (y), (z), (t) on a given trajectory. Possible cases are classified and one of them is analyzed.

Based on archival images from the Hubble Space Telescope, stellar photometry of the galaxy NGC 4068 was carried out. The resulting Hertzsprung-Russell diagram (CM diagram) shows branches of young and old stars. To estimate the metallicity of young stars, isochrones of different ages and metallicities were used. A combination of isochrones and the CM diagram of stars shows that the young stars of NGC 4068 have high metallicity, up to the metallicity of the Sun ((Z=0.02)). Since stars of high metallicity are observed throughout the body of the galaxy, we can talk about high metallicity of the entire galaxy, and not just one local region. The position of NGC 4068 among 105 irregular galaxies of different metallicities is shown on a diagram of the dependence between the metallicities of old and young stars. The almost linear dependence between these parameters indicates the absence of processes of rapid enrichment of galaxies with metals at the present stage of their evolution. The obtained results do not confirm the conclusion about the low metallicity of NGC 4068 reported earlier. For direct measurements of the metallicity of NGC 4068, the coordinates and fields of identification of the three brightest red supergiants with a high color index ((V-I)), which indicates their high metallicity, are presented.

In this paper, the first in a series of four articles, the scientific goals of the Metron project are highlighted, and the characteristics of the cosmic objects available for study within its framework are provided. The Metron interferometer radio telescope should include arrays of meter-range dipole antennas placed on Earth, in outer space, or on the far side of the Moon (or a combination of these options). Working in the meter range will enable the study of the so-called cosmological epoch of the ‘‘Dark Ages’’, which is challenging to observe but highly interesting for understanding the origin of the first stars, galaxies, and black holes, as well as for the search for new cosmological objects and processes. One possibility is to search for absorption in the 21-cm line within the extended halos around early protogalaxies and supermassive primordial black holes, whose existence is predicted in a number of models. Another goal of Metron may be to clarify the anomalous absorption in the 21-cm line previously detected by the EDGES telescopes and to observe radio emissions from the magnetospheres of stars and exoplanets. The Metron project aims to achieve unprecedented resolution in the meter range, which is expected to yield new world-class scientific results. Meter-range antennas and receivers are relatively simple and inexpensive, and the construction of interferometric arrays from them can be accomplished in a relatively short period of time.

The results of the analysis of 205 brightest sources ((S>15) mJy),which were found in the sky survey at the declination of thepulsar in the Crab Nebula, are presented. The survey was conductedat a frequency of 4.7 GHz using a three-beam radiometer complexinstalled in the focus of the Western Sector of the RATAN-600radio telescope in 2018–2019. Based on the measurements taken andthe data collected in the CATS astrophysical catalogs database,the radio spectra of the objects were constructed. For a quarterof all detected sources, data at frequencies above 4 GHz wereobtained for the first time, and for the rest they weresupplemented. The variability of radiation sources on the scalesof the year, from days to months, has been studied. The greatestchange in the radio flux was found in the blazar B2 1324(+)22. Thesearch for daily variability was carried out for 26 of thebrightest sources with an average value of (S_{4.7}sim 250) mJy.All sources are identified with objects fromoptical and infrared catalogs. The radio luminosity was calculatedfor 112 objects with known redshifts.

In the article, a method is developed for estimating the dynamic masses of the stellar and gas components of cluster-cloud systems under conditions of non-isolation and significant non-stationarity of stellar and gas subsystems in a regular field. A number of estimates of the dynamic masses of the stellar and gas components of the system are made without using the virial theorem for zero and positive values of the total energies (E) of the system as a whole and (E_{2}) of its gaseous subsystem. The well-known estimates of the free-fall time (tau_{textrm{ff}}) for fragments in the force field of a sphere of uniform and inhomogeneous density sphere simulating a system of gas and stars are refined. The estimates of the (tau_{textrm{ff}}) quantities are supplemented by estimates of the radial velocities (v_{r}) of the fragments in such systems. A number of relations between the parameters of the stellar and gas subsystems in the considered models of embedded clusters are obtained. It is shown that instead of one virial coefficient to describe the system, it is necessary to use three coefficients, the formulas for which are given. The relations make it possible to estimate the dynamic masses of non-isolated and non-stationary subsystems from data on the structural-dynamic characteristics of an embedded cluster. It is shown that the ratio ({overline{v}}_{c,1}^{2}/sigma_{1,v}^{2}>4), where (sigma_{1,v}^{2}) is the mean square of the velocities of the stellar subsystem in the case of its virial equilibrium, and ({overline{v}}_{c,1}^{2}) is the mean square of the critical velocities of the stars in this subsystem. It is shown that embedded clusters with parameters (x=R_{1}/R_{2}) and (mu=M_{1}/M_{2}) have maximum values ({overline{v}}_{c,1}^{2}/sigma_{1,v}^{2}) along some curve in the ((x,mu)) space ((M_{i}) and (R_{i}) are the mass and radius of the (i)th subsystem). The embedded clusters with parameters ((x,mu)) close to this curve are the least susceptible to destruction space relaxation processes. It is shown that, depending on the initial energies (E) and (E_{2}), the masses of a subsystem of stars in an embedded cluster can be much smaller than the virial masses of this subsystem. This result is also of particular interest for estimating the dynamic masses of galaxy clusters. It is noted that an increase in the degree of non-stationarity of the considered models of embedded clusters leads to a decrease in the periods of oscillations of the stellar subsystem.

To understand the nature of gas flows in star-forming regions of nearby galaxies, the relationship between the surface brightness values in the H(alpha) line and the velocity dispersion of ionized gas, known as the ‘‘surface brightness–velocity dispersion’’ diagram, is often used. Based on three-dimensional gas-dynamic calculations, we examined the evolution of synthetic diagrams for supershells formed as a result of multiple supernova explosions in a star cluster located in the galactic disk. Based on the results of a study of changes in the shape and structure of the diagram depending on the gas density, its metallicity, and the disk scale height, it is possible to identify ranges of values in the diagram that are characteristic of young bubbles developing in dense or rarefied gas at large heights above the plane of the disk. We found that the structure of the diagram depends on the age of the supershells and the physical properties of the gas in the disk. For nearby dwarf galaxies, the structure of the observed ‘‘surface brightness–velocity dispersion’’ diagrams can only be explained by describing the dynamics of bubbles formed by multiple SN explosions in small star clusters of different ages.

We present photometric and spectrocsopic observations of supernovae carried out with the 2.5-m telescope of the Caucasus Mountain Observatory of SAI MSU. The light curves for the objects 2017egm, 2017eaw, 2018cow, 2018aoq, 2018zd, 2019yvr, 2019vxm, 2020tlf, and 2020xtz were constructed and their basic parameters were determined. The observed light curves are compared to the theoretical calculations for SNe II-P 2017eaw and 2018aoq. The spectra of SNe 2019vxm, 2019yvr, 2020tlf, 2020xtz are presented. The profiles of emission lines are studied for SNe IIn 2019vxm and 2020tlf. Spectral modeling was carried out for SNe 2019yvr and 2020xtz. The results of the program of prompt SNe spectral classification for eight objects are reported.

We review the stellar magnetism studies published in 2022.We analyzed a total of 75 papers, which focus mostly on the study ofmagnetic fields in chemically peculiar and activecool stars. In the latter, migration of magnetic spots and changeof their configuration is observed. Projects of spectrographs andspectropolarimeters for new big telescopes are also presented.

The paper presents magnetic field measurements and physicalparameters for 96 stars. Observations were carried out in 2015with the 6-m BTA telescope using the Main Stellar Spectrograph(MSS). By analyzing circularly polarized spectra, the magneticfields of the stars HD 653, HD 8855, HD 94603, HD 188101(KIC 6065699), HD 189160,HD 195464, and BD+44({}^{circ}) 4130 were discovered for the first time.No systematic measurement errors were detected.

A study of the activity of a bright M-dwarf L 98-59, located at a distance of 10.6 pc from Earth is reported. The star has a multiplanetary system, where one of the planets, L 98-59 b, is a rocky planet with a mass not exceeding the mass of Venus. It was found that the level of chromospheric activity of L 98-59 does not exceed the average value characteristic of other cold dwarfs with similar color index values ((B-V)). This level is below solar, the mean (log R{{}^{prime}}_{textrm{HK}}) parameter for L 98-59 is equal to (-)5.297 dex. The data about the parent star and its activity was used to estimate the magnitude of the atmospheric escape of five planets (including the planet candidate 05). To calculate the loss of matter from the planetary atmospheres (without a detailed modeling of the processes in the ‘‘star–planet’’ system), we applied an approximation formula corresponding to the energy-limited atmospheric loss model. Estimates of the XUV photon flux—extreme ultraviolet (EUV) and X-ray photons for the medium and high activity levels, as well as the estimates of the tidal parameter (K_{textrm{tide}}(xi)) were found. Variations of the (dot{M}) parameter have been specified for five planets of the L 98-59 system, taking into account the possible activity level variations of the star. The (dot{M}) parameter variations for planets c–e range from (7.6times 10^{6}) g s({}^{-1}) to (3.8times 10^{7}) g s({}^{-1}) (average activity level) and (1.2)–(5.7times 10^{7}) g s({}^{-1}) (high activity level). For the planet L 98-59 b, the an analogue of Venus, we got the following estimates: (1.3times 10^{7}) and (2.0times 10^{7}) g s({}^{-1}) (for the intermediate and high activity levels, respectively). It can be assumed that the relatively modest outflow of matter from their atmospheres (dot{M}), despite the proximity of the planets to their star, is due to a small flux of XUV photons from the star due to the low level of its activity.