Astrophysical Bulletin最新文献

The optical spectra of ultraluminous X-ray sources (ULXs) show signs of powerful outflows of matter. These outflows are responsible for the formation of a significant portion of optical and ultraviolet emission in ULXs and can either be stellar winds of the donor stars or optically thick outflows (winds) from the surface of supercritical accretion disks. In the latter scenario the outflows are still expected to be similar to stellar winds of massive stars, which allows one to use the same methods for their study based on a comparison of the observed spectra with those simulated within the framework of non-LTE extended atmosphere models. In this paper, we simulate the optical spectrum of the ultraluminous X-ray pulsar NGC 7793 P13, assuming that its emission part is produced in the wind of the supercritical accretion disk. The estimated mass loss rate is about (1.4times 10^{-5}M_{odot}) yr({}^{-1}). We consider the positive and negative aspects of the model and also discuss the applicability of the concept of supercritical disk winds to NGC 7793 P13 and to another well-known ultraluminous X-ray pulsar, NGC 300 ULX-1.

We present a survey of the results of photometric and spectral observations of a nebula AFGL 2688 in the system of post-AGB star V1610 Cyg. Apart from the analysis of the published results, our new spectral observations of the star at the BTA over 2002–2022 are also given consideration. A new understanding of the kinematics of gas and dust in the lobes of the nebula has been obtained. The totality of published data, registered in a wide range of wavelengths, allows us to consider AFGL 2688 as a prototype nebula for the stars undergoing the post-AGB stage. An assumption on the variation of the chemical composition of the central star is made. We discuss the prospects for studying the object in the optical range.

We explain the details of the photometric operation mode of the ASTRONICAM near-IR spectrograph camera mounted on the 2.5-m telescope of the Caucasian Mountain Observatory of the Sternberg Astronomical Institute and describe algorithms used for primary correction and overall pipeline reduction of the acquired data. We present the transformation equations from the 2MASS photometric system to the instrumental (Y)-band system. We derive color transformation coefficients between the instrumental photometric system and standard MKO-NIR (Mauna Kea Observatories Near-Infrared) system for the (J), (H), and (K)-band filters and show that the camera system is close to the standard photometric system. We found that in the case of observations at zenith, average background brightness level, and (1^{primeprime}) seeing the stars with (J=22^{textrm{m}}), (H=20overset{textrm{m}}{.}5), (K=19overset{textrm{m}}{.}5) can be measured with a 3000-s exposure at the signal-to-noise ratio (SNR=3).

The observations and comprehensive study of intermediate initial mass stars at the late stages of evolution, and after the asymptotic giant branch (AGB) in particular, are of crucial importance to identify the common properties for the stars of given group and to reveal binaries among them. This work aims to investigate photometric and spectral peculiarities of a poorly studied post-AGB candidate and infrared source IRAS 07253–2001. We present the new multicolor (UBVR_{C}I_{C}YJHK) photometry obtained with the telescopes of the Caucasian mountain observatory and analyse it together with the data acquired by the All Sky Automated Survey for SuperNovae. We report on the detection of multiperiod brightness variability caused by pulsations. A beating of close periods, the main one of 73 days and additional ones of 68 and 70 days, leads to amplitude variations. We have also detected a long-term sine trend in brightness with a period of nearly 1800 days. We suppose it to be orbital and IRAS 07253–2001 to be binary. Based on new low-resolution spectroscopic data obtained with the 2.5-m telescope of the Caucasian mountain observatory in 2020 and 2023 in the (lambda) 3500–7500 wavelength range we have identified spectral lines and compiled a spectral atlas. We have found the [N II], [Ni II] and [S II] forbidden emission lines in the spectrum and discuss their origin. The H(alpha) line has a variable double-peaked emission component. We have derived preliminary estimates of the star’s parameters and detected a variation of radial velocity with a peak-to-peak amplitude of about 30 km s({}^{-1}).

We present observations of the vdB 130 cluster vicinity in a narrow-band filter centered at a (2.12,mu{textrm{m}}) molecular hydrogen line performed at the Caucasus Mountain Observatory of the Lomonosov Moscow State University. The observations reveal an H({}_{2}) emission shell around vdB 130, coincident with a bright infrared shell, visible in all Spitzer bands. Also, numerous H({}_{2}) emission features are detected around infrared Blobs E and W and in the vicinity of a protocluster located to the east of the shell, in a tail of a cometary molecular cloud. H({}_{2}) emission in the vicinity of the vdB 130 cluster is mostly generated in well-developed H II regions and is of fluorescent nature. In the protocluster area, isolated spots are observed, where H({}_{2}) emission is collisionally excited and is probably related to shocks in protostellar outflows. Obtained results are discussed in the context of possible sequential star formation in the vicinity of the vdB 130 cluster, triggered by the interaction of the expanding supershell surrounding the Cyg OB1 association with the molecular cloud and an associated molecular filament.

The paper presents results of calculating the RATAN-600 beam pattern (BP) and BP drift scans of point radio sources in the West Sector radio telescope operation mode at a frequency of 4.7 GHz. When calculating the BP, the properties of the radio telescope antenna system in this operation mode were taken into account: the use of a large secondary mirror, asymmetric radiation of the primary mirror, and the location of the primary feeds (feed horns) along the focal line of the secondary mirror. The shape of the calculated drift scans of sources through the BP is compared with that of the experimental drift scans of sources obtained from observations in the West Sector. The main characteristics of the drift scans are calculated and compared when the radio telescope operates with the West and North Sectors. A new method for determination of flux densities of sources passing through the BP outside its central cross-section is proposed, and its accuracy is estimated.

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.