Astrophysical Bulletin最新文献

There are indirect signs of the presence of a companion near the star CQ Tau. A period of 10 years was found in the brightness variations. The image of the disk shows an extensive cavity with a size of about 25 AU, surrounded by a dust ring with a distribution maximum near 53 AU. A simulation of the interaction of dust and gas in the vicinity of a star with CQ Tau parameters was carried out assuming the existence of a companion in an orbit with a period of 10 years. It was shown that an M-type star in a highly elongated orbit is capable of forming a region of reduced density around the center of mass of the system, with a size close to the one observed. However, the dust ring-like structure in this case is located noticeably closer to the star than observed. Evidence has been obtained that a massive planet in an outer elongated orbit, could form a ring-shaped dust structure at a distance similar to that observed.

The wind-fed accretion of gas with an intrinsic magnetic field onto neutron stars in high-mass X-ray binaries (HMXBs) is discussed. The criteria for the implementation of quasi-spherical accretion in the system, the formation of a Keplerian accretion disk and a non-Keplerian magnetically arrested disk (MAD-accretion scenario) are formulated. It is shown that the period of the equilibrium rotation of a neutron star in the MAD-accretion scenario, in addition to the parameters of the binary system, is also determined by the velocity, temperature, and degree of magnetization of the stellar wind of its massive companion. Within the hypothesis of the equilibrium rotation, we have estimated the parameters of the stellar wind for the most fully-studied quasi-equilibrium accreting pulsars in the HMXBs corresponding to the criteria for the MAD-accretion scenario implementation. We show that the period of the equilibrium rotation of a neutron star in the system, all other things being equal, increases with the growth of the magnetization degree of the stellar wind component of its massive companion flowing out in the plane of the system’s orbit. Therefore, the periods of accreting pulsars in systems with similar parameters can differ from each other by several orders of magnitude and, under favorable conditions, reach values of several thousand and even tens of thousands of seconds.

A particular case of a local integral, published by Shamshiev in2024, leads asymptotically to a potential with almost sphericalsymmetry at large distances (r). The (L(x,y,z)=textrm{const}) surfaces, which give the boundaries of the area ofmotion and are close to spheres, are found.

The electric vector position angle exhibits significant changes over time in most blazars. Sometimes these changes occur in an orderly fashion—such events are commonly referred to as rotations. This study examines a method for detecting and analyzing these rotations through cross-correlation analysis. The proposed method is evaluated using a series of model examples, from the most straightforward to those that mimick behaviors observed in real objects. For the simplest models, some analytical results have been obtained. The analysis showed that the proposed method, except for trivial cases, is likely not suitable for effectively detecting and studying rotations.

The initial power spectrum of density perturbations, generated during the inflationary epoch, is now constrained by observations on scales of (lambda>5) Mpc and has a power-law form. The peculiarities of the inflationary process can lead to the appearance of non-power-law contributions to this spectrum, such as peaks. The exact size and shape of the peak cannot be predicted in advance. In this paper, we propose methods for searching for such peaks in the region of the spectrum with (lambda<5) Mpc. Perturbations on these scales enter the nonlinear stage at (zgtrsim 10), which is now becoming accessible to observations. Our studies of numerical models of the large-scale structure with peaks in the initial spectrum have shown that spectral features on scales of (lambda>0.1) Mpc manifest in the clustering of galaxies, as well as affect their mass function, sizes, and density. Studying these characteristics of distant galaxies will allow us to constrain cosmological models with peaks.

DDO 68 is a star-forming (SF) dwarf galaxy residing in a nearby void. Its gas metallicity is among the lowest known in the local Universe, with the (12+log(textrm{O/H})) parameter in the range of 6.96–7.3 dex. Six of its SF regions are located in or near the so-called ‘‘Northern Ring’’, in which the Hubble Space Telescope (HST) images reveal many luminous young stars. We present for these SF regions (Knots) the results of optical monitoring in 35 epochs during the years 2016–2023. The data was acquired with the 6-m (BTA) and 1-m telescopes of the Special Astrophysical Observatory, and the 2.5-m telescope of the MSU Caucasian Mountain Observatory. We complement the above results with the archival data from 10 other telescopes for 11 epochs during the years 1988–2013 and with three our BTA observations between 2005 and 2015. Our goal is to search for variability of these Knots and to relate it to the probable light variations of their brightest stars. One of them, DDO 68-V1 (in Knot 3), was identified in 2008 with a luminous blue variable (LBV) star born in the lowest metallicity environments. For Knot 3, variations of its integrated light in the previous epochs reached about (0overset{textrm{m}}{.}8). In the period since 2016, the amplitude of the variations in Knot 3 has reached about (0overset{textrm{m}}{.}3). For the rest of the Knots, due to the lower amplitudes, the manifestation of variability is less pronounced. We examine the presence of variability via the (chi^{2}) criterion and the Robust Median Statistics and discuss the robustness of the detected variations. The variability is detected according to both criteria in the light curves of all Knots with the (chi^{2}) confidence level at (alpha=0.0005). The peak-to-peak amplitudes of the variations are approximately (0overset{textrm{m}}{.}09), (0overset{textrm{m}}{.}13), (0overset{textrm{m}}{.}11), (0overset{textrm{m}}{.}08), and (0overset{textrm{m}}{.}16) for Knots 1, 2, 4, 5, and 6, respectively. The amplitudes of the related variations of the brightest supergiants in these regions can reach about (3overset{textrm{m}}{.}0).

Gravitational waves are ‘‘ripples’’ in space-time caused by some of the most violent and energetic processes in the Universe. A study of gravitational waves GW150914 and GW170104 was carried out using strain data from LIGO (Laser Interferometer Gravitational Wave Observatory). The analysis presented is consistent with the published results on the subject. It was found that both systems produced gravitational waves from a pair of inspiraling black holes that approached very closely before merging. Different properties of the systems like chirp mass, compactness ratio, luminosity distance, eccentricity, redshift, and spin parameter were studied and the nature of the system was identified from the results.

Using observations of M 74 X-1 obtained with the Chandra X-ray Observatory and the Hubble Space Telescope, we identified this source in the optical range. Analysis of other archival data allowed us to track the evolution of M 74 X-1 over two decades of observations, as well as to search for a correlation between the object’s variability in the X-ray and optical ranges based on several available quasi-simultaneous observations. As a result, we revealed an approximately linear decrease in the object’s brightness of about (1overset{textrm{m}}{.}9) in the (V) band in the 2005–2021 time range, which is atypical for most ultra-luminous X-ray sources, and, presumably, is not caused by a change in the X-ray luminosity of the object. At the same time, we found changes in the nature of the short-term X-ray variability of M 74 X-1: by 2021, the stochastic variability of the object decreased and the quasi-periodic oscillations on a timescale of about 1.5 hours seen in observations of 2001–2002 disappeared.

We present a study of the radio and optical properties of the high-frequency peaker (HFP) blazar PKS 1614(+)051 at (z=3.21) based on the data covering the time period of 1997–2024. The radio data are represented by the instantaneous 1–22 GHz measurements from the SAO RAS RATAN-600 radio telescope, the 5 and 8 GHz data from the IAA RAS RT-32 telescopes, and the 37 GHz data from the RT-22 telescope of CrAO RAS. The optical measurements in the (R) band were collected with the SAO RAS 1-m Zeiss-1000 and 0.5-m AS-500/2 telescopes, and the ZTF archive data. We have found low overall variability indices (0.1–0.2) and a median spectral peak at 4.6 GHz, which is stable during the long-term period of monitoring. An analysis of the radio light curves reveals significant time delays (0.6 to 6.4 yrs) between the radio frequencies along with variability timescales ranging from 0.2 to 1.8 yrs in the source’s rest frame, which is similar to the blazars at lower redshifts. Spectral modeling suggests the presence of both synchrotron self-absorption (SSA) and free-free absorption (FFA) processes. Based on the SSA model, we provide estimates of the magnetic field strength which peaks at approximately 100 mG. A spectroscopic study with the BTA SCORPIO-1 spectrograph has found evidence of the regular motion of a neutral hydrogen envelope around the blazar center, which confirms the presence of a sufficient amount of gaseous matter to form an external FFA screen. The results highlight the importance of multi-wavelength and long-term monitoring to understand the physical mechanisms driving the variability in high-redshift blazars.