Astrophysical Bulletin最新文献

The morphology and kinematics of the matter in the vicinity ofyoung stars ZZ Tau and ZZ Tau IRS are studied. It has been foundthat the emission nebula (the H(alpha) filament) locatedsouthwest of these stars, as well as the Herbig–Haro objectHH 393 projected onto it are moving away from ZZ Tau andZZ Tau IRS with a radial velocity of about 50 km s({}^{-1}). On theinner edge of the western part of the H(alpha) filament, there isa cooler filament emiting in the molecular hydrogen line((lambda=2.12) (mu)m) and in the dust continuum. In thenortheastern part of the studied region, a new Herbig–Haro objectis discovered and assigned the number HH 1232. The presence ofseveral more new emission nebulae is suspected. The electrondensity in the studied regions of the H(alpha) filament, as wellas HH 393 and HH 1232 (N_{e}lesssim 100) cm({}^{-3}). Arguments arepresented in favor of the fact that the dusty disk wind hascreated a gas-and-dust nebula around ZZ Tau IRS, along thesymmetry axis of which there is a jet moving in the direction ofHH 393.

The paper presents results of studying the kinematics of the ionized gas in the galaxy of the Large Magellanic Cloud type NGC 7292 obtained with the 2.5-m telescope of the Caucasian Mountain Observatory (CMO SAI MSU) and the 6-m BTA telescope of the Special Astrophysical Observatory (SAO RAS). Analysis of the velocity fields of the ionized and neutral hydrogen showed that the kinematic center of NGC 7292 located at the center of the bar, northwest of the photometric center of the galaxy (the southeastern end of the bar) previously taken as the center of NGC 7292. In addition to the circular rotation of the gas, the radial motions associated with the bar play a significant role in the kinematics of the disk. The observed perturbations of the gaseous-disk kinematics induced by the ongoing star formation do not exceed those caused by the bar. It is possible that part of the non-circular motions (at the southeastern end of the bar which is the brightest H II region) may be related to the effects of the capture of a dwarf companion or a gaseous cloud.

We performed photometric observations of the S 255, S 257, S 140, NGC 7358, and the Orion Bar photo-dissociation regions (PDRs) at 2 (mu)m using narrow-band filters centered on the Br(gamma), H({}_{2}), and [Fe II] lines, as well as the narrow-band (K_{textrm{cont}}) and the broad-band (H) filters for continuum subtraction. The observations were done with the 2.5-m telescope of the SAI Caucasian Mountain Observatory and the near-infrared camera and spectrograph ASTRONIRCAM. We find several high-density arc-like structures in the Br(gamma) and [Fe II] images of the ionized gas in NGC 7538 and extended shells and arcs visible through the H({}_{2}) emission. The H ionization front and H({}_{2}) dissociation front are merged in NGC 7538. In S 255 and S 257 we detected only Br(gamma) emission from the H II regions and bright H({}_{2}) emission from the PDRs. The projected distance between the H ionization and H({}_{2}) dissociation fronts is approximately 0.3–0.4 pc, which cannot be explained using models of a uniform medium. Most probably, the ionized and neutral gas in these PDRs is clumpy. The H I-to-H({}_{2}) transitions in the NGC 7538, S 255, S 257 and S 140 PDRs are gradual with no sharp borders. This conclusion also agrees with the suggestion of a clumpy medium.

The paper presents the first results of the ongoing spectropolarimetric monitoring of magnetic fields of stars, whose chemically peculiar nature has been previously revealed with the 1-m SAO RAS telescope. We selected the sample candidates using the photometric data of the Kepler and TESS space missions. The efficiency of the method of searching for new CP stars based on photometric light curves has been confirmed. We present the magnetic field measurements and estimate the atmospheric parameters of the objects under study.

In 2022 we carried out an upgrade of the speckle polarimeter (SPP)—the facility instrument of the 2.5-m telescope of the Caucasian Observatory of the SAI MSU. During the overhaul, CMOS Hamamatsu ORCA-Quest qCMOS C15550-20UP was installed as the main detector, some drawbacks of the previous version of the instrument were eliminated. In this paper, we present a description of the instrument, as well as study some features of the CMOS detector and ways to take them into account in speckle interferometric processing. Quantitative comparison of CMOS and EMCCD in the context of speckle interferometry is performed using numerical simulation of the detection process. Speckle interferometric observations of 25 young variable stars are given as an example of astronomical result. It was found that BM And is a binary system with a separation of 273 mas. The variability of the system is dominated by the brightness variations of the main component. A binary system was also found in NSV 16694 (TYC 120-876-1). The separation of this system is 202 mas.

Homogeneous and complete samples of brown dwarfs are needed for various kinds of studies: kinematic studies of the Galaxy, studies of binary stars with brown dwarfs, refinement of the low-mass end of the initial mass function, etc. According to various estimates, brown dwarfs can make up to 25% of the population of the Galaxy; however, the discovery of brown dwarfs with spectroscopic methods is extremely labor-intensive. In this paper, we present the cross-identification of the known nearest brown dwarfs from the 2021 list with the DES optical survey and the creation of photometric rules based on the detection of brown dwarfs in three surveys: WISE, 2MASS, and DES. Moreover, we present different photometric rules for each of the three families of brown dwarfs: bright, transit, and faint. No such division has been made yet.

We study the dependence of the kinematic properties of the subsystems of Galactic open clusters on their ages. It was found that the angular velocity of Galactic rotation in the solar vicinity decreases to 25.6 km s({}^{-1}) kpc({}^{-1}) for clusters older than 600 Myrs. According to the rotation curves of the Galaxy for different age intervals at a galactocentric distance of 6.0 to 13.0 kpc, it is found that older open clusters rotate much more slowly than young and middle-aged clusters. The rotation curve decreases with increasing galactocentric distance in the entire distance interval under consideration. We can observe the separation of open clusters into thick and thin disk objects. A near-sinusoidal dependence of the radial cluster velocity component on galactocentric distance is obtained for distances ranging from 6.0 to 13.0 kpc. No dependence of the vertical velocity component on galactocentric distance is found.

We have been carrying out daily observations of bright microquasars at 1.2–20 GHz with the Northern sector of the RATAN-600 radio telescope for more than ten years. During the 2019–2021 observations we detected bright flares, which we call giant flares because fluxes reach record levels—above 20 Jy—during these events. In this paper we report the results of intraday variations of the microquasar Cygnus X-3 in multi-azimuth observations made with the ‘‘Southern sector with a flat-sheet reflector’’ during giant flares of Cygnus X-3. These were the first such observations made simultaneously at several frequencies on a short time scale (10 minutes). Observational data consists of 31 measurement made within (pm)2.7 hours of the culmination of the object. We are the first to discover the evolution of the spectrum of the flare emission of Cygnus X-3 on a time scale comparable to the orbital period of the binary. The measurement data allowed us to determine the temporal and spectral parameters of radio emission, which are typical for synchrotron flare emission in relativistic jets. Evolution of the radio emission of X-ray binaries on short time scales is a key to understanding the formation of jet outbursts in the process of mass accretion of the matter of the donor star onto the relativistic object.

We report the results of a study of spot activity manifestations in 11 K-type dwarfs with established planets in the habitable zone according to the data from the Kepler space telescope archive acquired during 90-day long Q3-set observations. We found that the spot area (A) on the surface of K-type dwarfs of our list is greater than the characteristic solar value, but is comparable to the maximum levels observed for the Sun, except for the active star KIC 9351316 with (A=7588) MSH. We performed a detailed study of the K-type dwarf KIC 5938970 (Kepler-1540) with flare activity higher than that of the Sun and flare energy (log E) spanning the 32.95–34.48 interval. We estimated the rotation period of the star, (P=15overset{textrm{d}}{.}1447), and its parameter (DeltaOmega=0.024pm 0.007) rad/day. Based on the Kamogata Wide-field Survey data (99 (V)-band magnitude estimates in 3310 days) we conclude that photometric variations include cyclic changes and a weak monotonic brightness increase. The characteristic periods of possible cycles are equal to 2.8 and 4.4 years. Our study of the star’s activity in about half of the currently known K-type dwarfs with planets in the habitable zone (11 objects among 17 stars in the complete list) based on high-precision observations made with the Kepler telescope revealed certain activity manifestations (high flare activity in one star, high spot activity in another, etc.). We conclude that a detailed study of activity manifestations in each particular star is highly desirable when studying planetary systems of K-type stars including planets in the habitable zone.

The paper presents the results of calculations using anapproximate approach to estimating the thermal loss of theatmosphere of a hot exoplanet. The objective of simulation was tostudy a system of a yellow dwarf of the spectral type G with anexoplanet like a hot sub-Neptune or super-Earth. Estimates of theatmospheric loss rate for a hot sub-Neptune in weakly and stronglyelliptical orbits are obtained. Calculations have shown that theatmospheric loss (dot{M}_{T}) averaged over the orbital period ofthe model hot sub-Neptune varies from (5.8times 10^{17}) g for anorbit with (e=0.0) to (2.6times 10^{18}) g for an orbit with(e=0.8), that is, it increases by almost 4.5 times. Moreover, for(e=0.2,0.4,) and (0.6) the values of (dot{M}_{T}) are equal to(6.3times 10^{17}) g, (7.6times 10^{17}) g, and (1.2times 10^{18}) g respectively. Using the average atmospheric massloss per orbit, we can approximately estimate the time of totalatmospheric escape of the considered sub-Neptune—at (e=0.0),this time is approximately equal to 0.32 billion years, and at(e=0.8)—approximately 0.07 billion years. Accordingly, we canconclude that the initial ellipticity of the hot exoplanet’s orbitis an important factor in estimating the loss rate of the primaryhydrogen-helium atmosphere for sub-Neptunes and super-Earths.