Astrophysical Bulletin最新文献

This work is a continuation of the work of Kopylova and Kopylov published in 2016 on constructing the fundamental plane (FP) of groups and clusters of galaxies. In this article, the sample of galaxy systems has been increased from 94 to 172 objects. We have studied the relationships between the main characteristics of groups and clusters of galaxies using archival data from the SDSS, 2MASX, and NED catalogs. The measured parameters ((log L_{K}), (log R_{e}) and (logsigma)) of galaxy clusters define the fundamental plane in the near-infrared region: (L_{K}propto R_{e}^{0.77pm 0.09}sigma^{1.44pm 0.12}). The shape of the FP of groups and clusters is consistent with the FP of early-type galaxies (SDSS, (r)-filter), determined in the same way. Regression against (log R_{e}) in kpc gives the projection of the FP: (log R_{e}=0.98(pm 0.06),logsigma-0.56(pm 0.04)langlelog I_{e}rangle+3.57(pm 0.07)), which can be used to determine the distances of galaxy systems. The (rms) scatter of the zero point is 0.07, which is equivalent to a 16(%) error in determining the distance to a group or cluster of galaxies. For the first time, we have determined the average relative FP distances and peculiar velocities of five large superclusters of galaxies. According to our estimates, the average peculiar velocity of these superclusters relative to the CMB is (+75pm 360) km s({}^{-1}).

The light curves for almost 50 thousand stars with magnitudes (min[11overset{textrm{m}}{.}5,19overset{textrm{m}}{.}5]) have been obtained over 2.5 years at SAO RAS in the process of conducting an exoplanet survey in roughly (1overset{circ}{.}5)-sized fields around the white dwarfs WD 0009(+)501 and GRW (+)708247. In this paper we present a catalog of variable stars that have been found in the considered regions. Periodogram analysis was used as the main variation search method. The catalog includes 150 periodic variable stars: 113 of them have been known previously, and for the remaining 37 variations have been discovered for the first time. These stars were classified according to the nature of the variations into four eclipsing variable and three pulsating types, as well as rotating stars. We present the periods and variation amplitudes in the range of (Pin[0overset{textrm{d}}{.}036,32overset{textrm{d}}{.}14]) and (Delta min[0overset{textrm{m}}{.}0064,1overset{textrm{m}}{.}45]), determined from the investigated data.

The problem caused by the inconsistency between the age and spin-down time scale of the white dwarfs in the systems AR Sco and AE Aqr is discussed within the hypothesis of their accretion-driven spin-up during the previous epoch. Considering a scenario of accretion from a Keplerian disk, we conclude that the white dwarfs in these systems could be spun-up to the currently observed periods provided the radius of their magnetospheres at the spin-up phase was substantially smaller than the Alfven radius. We show that the required magnetospheric radius value can be reached if the accretion flow penetrates the magnetic field of the white dwarf at its magnetospheric boundary due to anomalous (Bohm) diffusion. In this case the spin-up of the white dwarfs in the systems under consideration can be described based on a model of stationary accretion from the Keplerian disk at an average rate of (10^{-9}{-}10^{-8}M_{odot}) yr({}^{-1}) without any additional assumptions about the evolution of the intrinsic magnetic field of the white dwarfs during the spin-up phase.

The article presents the results of long-term photometric monitoring of two binary gravitationally lensed quasars, SDSS J2124(+)1632 and SDSS J0806(+)2006, carried out at the Maidanak Observatory in 2017–2022. The obtained light curves of the lensed components of both systems are analyzed. The variability of SDSS J2124(+)1632 turned out to be quite large: up to (0overset{textrm{m}}{.}50) for the system as a whole and up to (0overset{textrm{m}}{.}75) for component A. Long-term microlensing was found against the background of a general increase in the apparent brightness of the quasar source. The brightness variations in SDSS J0806(+)2006 are less intense: the range is about (0overset{textrm{m}}{.}20) for the system as a whole, and up to (0overset{textrm{m}}{.}25) for both components. Analysis of the light curves did not show the presence of microlensing here. We also calculated the probable values of the time delay: (Delta t_{textrm{AB}}=102pm 20) days (component B is in the lead) and (Delta t_{textrm{AB}}=-53.0pm 6.0) days (component A is in the lead) in SDSS J2124(+)1632 and SDSS J0806(+)2006, respectively. The value of (Delta t_{textrm{AB}}) for SDSS J2124(+)1632 is consistent with previously found time delays for binary gravitationally lensed systems. In the case of the second system, the time delay is consistent with earlier theoretical calculations, which suggested that the time delay should be about 50 days.

Chemically peculiar (CP) stars of early spectral types are the only Main-Sequence objects of the Hertzsprung–Russel diagram that have strong magnetic fields covering the entire surface of a star and maintaining a stable structure on a scale of at least decades. The origin and evolution of magnetic fields of CP stars are still a subject of discussion, despite significant progress in the field of observation of stellar magnetic fields and their theoretical description. This situation has developed not least because of the problem of accurately determining the age of CP stars. We performed a review of magnetic fields of CP stars in the Orion OB1 association and five intermediate-age clusters ((alpha) Per, Pleiades, NGC 7092, and IC 4756) and found evidence of a strong decrease in the proportion and strength of magnetic fields of CP stars relative to normal stars of the same spectral types. The found dependences can serve as confirmation of the fossil nature of large-scale magnetic fields of stars. The conclusions of this paper are based on the measurements of more than 800 spectra obtained in the period from 2013 to 2023 with the Main Stellar Spectrograph of the 6-m BTA Telescope for about 100 stars.

All available photometry for the Cepheid KN Cen is analyzed to construct its ((O-C)) diagram spanning a 134-year long time interval. This made it possible for the first time to compute the rate of evolutionary period increase of the Cepheid, (dP/dt=+2.91(pm{1.68})) s yr({}^{-1}), which is consistent with the results of model computations for the third crossing of the instability strip. The test for stability of pulsations proposed by Lombard and Koen confirmed the reality of the evolutionary period change.

In this paper, we analyze the apparent surface density observations of 81 globular clusters provided by Gaia DR2. The problems of analyzing these observations and their differences from similar data obtained using the HST are discussed. Based on the results of this analysis of the quality of observational data and a number of physical considerations, we separate globular clusters into three classes and then consider the issues of modeling the apparent surface density versus distance. The values of the free parameters of the model are found by the symplectic minimization method. The free parameters including the concentration parameter are for the first time found using the 4-parameter generalized model we propose.

We present the results of analyzing the activity manifestations of the K3 V spectral type dwarf HIP 113103 (HD 216530) and estimate the matter loss from the atmospheres of two of its planets. HIP 113103 can be classified as a relatively young object with an age of about 470 million years—1 billion years. Using the standard method, based on the observed data from the TESS mission, we estimated the areas of spots on the surface of the star, which exceed the maximum area of spots on the Sun and are 6100 and 4950 MSH for sectors 1 and 28, respectively. According to the data from the observation archive of the All Sky Automated Survey, the activity cycles of HIP 113103 have been established to last about 610, 825, and 1030 days (1.7, 2.3, and 2.8 years, respectively). Both planets in the stellar system HIP 113103 are characterized as objects with radii of 1.829(R_{oplus}) and 2.400(R_{oplus}), with periods of 7.6 and 14.2 days, respectively, lying on opposite sides of the Fulton Gap in the ‘‘Period—Radius’’ diagram. The loss of matter from the planetary atmospheres was calculated using an approximation formula corresponding to the energy-limited atmospheric loss model. To estimate the flux of XUV photons, analytical dependences were used connecting flux values and the (log R^{prime}_{textrm{HK}}) parameter. It was found that the values (dot{M}) values for planets b and c are equal to (2.8times 10^{8}) g s({}^{-1}) and (1.9times 10^{8}) g s({}^{-1}), respectively. The planet HIP 113103 b attracts special attention because, with its radius (R_{p}=1.829R_{oplus}), it belongs to a small population of planets with the radii (1.5R_{oplus}<R_{p}<2.0R_{oplus}), which characterizes the evolution of super-Earths and mini-Neptunes. HIP 113103 c has a radius of (R_{p}=2.40R_{oplus}) and an equilibrium temperature of (585pm 10) K which characterizes the object as an already established warm mini-Neptune. A comparison of the properties of planets b and c is of interest, since they belong to the same system, are irradiated by the same star, probably have similar ages and conditions of formation, etc.

The age estimates of magnetic stars obtained from the ages of clusters and associations are compared with those determined using the grids of evolutionary paths and isochrones separately for each star. Large deviations between the age systems have been discovered. Analysis of the studies that use ‘‘cluster’’ ages shows that they differ significantly from those obtained using individual estimates.

A method for radiometer-noise generation and its software implementation in the form of a Python library module is proposed. The method can be used to simulate radiometer noise with variable component properties: Gaussian white noise and flicker noise (random drift) with a power spectrum linearly increasing with decreasing frequency. The method is based on the transformation of spectral properties of Gaussian noise via sequential filtering by a differentiator, nonlinear threshold switch, and subsequent integration. By changing the integrator accumulation time constant and the threshold level relative to noise intensity (sigma) one can change the resulting form of the spectrum and the corresponding statistical parameters of the output noise over a wide range: from stationary white noise to noise dominated by a (1/f)-type spectrum component. Empirical polynomial approximation formulas for the dependence of the spectral index of the resulting noise records on the nonlinear threshold switch level in the 0.0–(3.5sigma) interval are derived based on numerical simulations using a software implementation of the model. Examples of noise-record implementations, their spectra, and autocorrelation functions are demonstrated. The generated noise is shown to be similar to the noise observed on radio telescopes of the Institute of Applied Astronomy of the Russian Academy of Sciences.