Astrophysical Bulletin最新文献

We report the results of optical spectroscopy of eight highly variable X-ray sources—AGN candidates from all-sky survey of the eROSITA telescope of the Spectrum-Roentgen-Gamma Space Observatory—performed with the TDS spectrograph (3600–7500 Å, (Rapprox 2000)) attached to the 2.5-m telescope of the Caucasian Mountain Observatory of Sternberg Astronomical Institute of M.V. Lomonosov Moscow State University. We determined the redshifts of the sources from the emission and absorption lines in their spectra. At least five objects can be classified as Seyfert galaxies. We performed pilot infrared photometry of three distant quasars with (z>5) using the ASTRONIRCAM camera and show that on the ‘‘((z-J){-}(J-W1))’’ diagram the distant quasars studied can be confidently distinguished from Galactic red and brown dwarfs. This result proves the possibility of preliminary classification of distant X-ray quasar candidates by their IR colors for further detailed spectroscopic study on large telescopes.

This review presents the results of observations of high-mass and low-mass X-ray binaries carried out at the Caucasus Mountain Observatory of SAI MSU over the past five years. Interpretation of these observations within the framework of complex unconventional models has led to a number of interesting results. In particular, on the basis of the secular evolutionary increase in the orbital period of the microquasar SS 433 that we discovered, we managed to prove that the relativistic object here is a black hole, and the SS 433 system itself evolves as a semi-detached system due to the fact that the distance between its components increases with time, which prevents the formation of a common envelope. In the microquasar Cyg X-3, an anomalous behavior of IR color indices with the phase of the orbital period was detected. Modeling is carried out and estimates of the parameters of this system are given. In low-mass X-ray binaries (X-ray novae), black hole masses are estimated, spectra of advection-dominated disks are constructed, and an observational justification is given for modern results of three-dimensional gas-dynamic calculations for interacting binaries.

The results of the analysis of photometric and spectral monitorings of the recurrent symbiotic nova T CrB, carried out using the low-resolution spectrograph TDS of the 2.5-m telescope and the CCD photometer of the 0.6-m telescope of the CMO SAI, are presented. It is shown that the fluxes in the emission lines H(alpha), H(beta), He I (lambda) 5876 change by 6–16(%), and in the emission line He II (lambda) 4686 by about 60(%) on timescales of 20–60 minutes. The line flux curves on August 25, 2020 are similar to the (B) light curve of T CrB, but with a time delay of up to 600 s for different lines. The observed spectrum is approximated by the radiation of the system components with the following parameters: a red giant of spectral type M4 III, a nebula with (T_{e}=10^{4}) K and emission measure of (4times 10^{58}) cm({}^{-3}), and the accretion disk with (R_{1}=0.003R_{odot}), (R_{textrm{out}}approx 1R_{odot}) (at inclination (i=57^{circ})).

We present results of studying star-forming rings in six lenticular galaxies obtained with the narrow-band photometry in the H(alpha) and [N II] (lambda) 6583 emission lines using the MaNGaL tunable-filter mapper at the 2.5-m telescope of CMO of SAI MSU. The gas excitation mechanism estimated from the relation of the H(alpha) and [N II] (lambda) 6583 line fluxes occurred to be inhomogeneous along the ring: three outer rings have narrow segments of position angles, in which shocks waves dominate in the ring. Since the nature of the rings is most likely accretionary, the location of shock excitation in the outer rings indicates the direction of arrival of the external gas inflow. Star formation events in the rings are probably quite brief and effective: we mainly observe homogeneous sub-solar metallicity of the gas close to the level of local saturation of the gas chemical evolution in the star formation process and switching of the localization of the star-forming sites on a time scale of about 100 Myr. In NGC 932, we have caught the very beginning of the external gas accretion: there is still little of it in the galaxy, and the metallicity of the gas in the star-forming ring has not yet reached saturation.

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.