Astrophysical Bulletin最新文献

A study of the activity of a bright M-dwarf L 98-59, located at a distance of 10.6 pc from Earth is reported. The star has a multiplanetary system, where one of the planets, L 98-59 b, is a rocky planet with a mass not exceeding the mass of Venus. It was found that the level of chromospheric activity of L 98-59 does not exceed the average value characteristic of other cold dwarfs with similar color index values ((B-V)). This level is below solar, the mean (log R{{}^{prime}}_{textrm{HK}}) parameter for L 98-59 is equal to (-)5.297 dex. The data about the parent star and its activity was used to estimate the magnitude of the atmospheric escape of five planets (including the planet candidate 05). To calculate the loss of matter from the planetary atmospheres (without a detailed modeling of the processes in the ‘‘star–planet’’ system), we applied an approximation formula corresponding to the energy-limited atmospheric loss model. Estimates of the XUV photon flux—extreme ultraviolet (EUV) and X-ray photons for the medium and high activity levels, as well as the estimates of the tidal parameter (K_{textrm{tide}}(xi)) were found. Variations of the (dot{M}) parameter have been specified for five planets of the L 98-59 system, taking into account the possible activity level variations of the star. The (dot{M}) parameter variations for planets c–e range from (7.6times 10^{6}) g s({}^{-1}) to (3.8times 10^{7}) g s({}^{-1}) (average activity level) and (1.2)–(5.7times 10^{7}) g s({}^{-1}) (high activity level). For the planet L 98-59 b, the an analogue of Venus, we got the following estimates: (1.3times 10^{7}) and (2.0times 10^{7}) g s({}^{-1}) (for the intermediate and high activity levels, respectively). It can be assumed that the relatively modest outflow of matter from their atmospheres (dot{M}), despite the proximity of the planets to their star, is due to a small flux of XUV photons from the star due to the low level of its activity.

The paper is devoted to the analysis of the variability of the (gamma) Cas-type star HD 45995 in both optical and X-ray ranges. The variability of the line profiles of HD 45995 has been detected both for long (350–380 days) and short (11–87 minutes) time ranges. Based on the photometric light curves of HD 45995 obtained with the TESS satellite, we refined the rotation period of the star at (P=0.8443pm 0.0009) days. These light curves reveal components with periods of about 11({{}^{textrm{h}}}) typical for non-radial pulsations of B stars and components with periods of about 4–14 days, the nature of which is still unknown. We must note, that the latter components may be of an instrumental character, for example, due to the satellite drift. The pattern of the photometric variability, according to the TESS data, changes significantly for different observation epochs in 2018/2019 and 2020/2021. In the X-ray light curves of HD 45995, the presence of superfast variations with a period of (P=48.5pm 0.5)seconds is suspected.

We present the results of spectral observations and consequent analysis of six long-period double-lined eclipsing binaries (DLEBs) with main-sequence (MS) components from a sample formed with the aim of testing the ‘‘mass–luminosity’’ relation (MLR) for stars in the (M/M_{odot}>1.5) mass range. We analyzed all the obtained spectra using a technique that allows one to reveal the binary nature of the system and determine (T_{textrm{eff}}) and (log g) for each component, as well as the system metallicity [Fe/H] and line-of-sight extinction (E(B-V)). We computed the absolute parameters of the systems under consideration. An analysis of the obtained spectra shows that for three of the six objects (V1156 Cyg, EU Gem and V733 Per) we can clearly establish their binary nature and determine the spectral type and class for each component. Both components of the V733 Per system have already left the MS, and therefore the system must be excluded from our sample, whereas studies of V1156 Cyg and EU Gem should continue. OT And did not demonstrate a binary spectrum, however, the main component of the system is a hot A6 V star, and therefore, OT And should remain in our sample. We also revealed no binarity in the IM Del and LX Gem systems. Their brighter components turned out to be a cool giant and a supergiant, and these systems should be excluded from the sample based on the results of our analysis. We used the same technique to analyze the two spectra obtained for systems EU Gem and LX Gem using LAMOST. We have shown that the parameters determined from LAMOST spectra are in good agreement with the parameters determined for spectra obtained at the Caucasian Mountain Observatory (CMO) of SAI MSU. Our analysis allowed us to plot a first approximation of the V1156 Cyg velocity curves and show that the cool component in this system has a larger mass.

The development of a corrector for low-frequency variations in the star image at the input of ESPriF—the echelle spectropolarimeter of the BTA primary focus—is reported. New technical solutions have made it possible to extend the operating frequency range to 10 Hz for stars brighter than (13^{mathrm{m}}).

Study of high-redshift radio galaxies (HzRGs) can shed light on the active galactic nuclei (AGNs) evolution in massive elliptical galaxies. The vast majority of observed high-redshift AGNs are quasars, and there are very few radio galaxies at redshifts (z>3). We present the radio properties of 173 sources optically identified with radio galaxies at (zgeq 1) with flux densities (S_{1.4}geq 20) mJy. Literature data were collected for compilation of broadband radio spectra, estimation of radio variability, radio luminosity, and radio loudness. Almost 60(%) of the galaxies have steep or ultra-steep radio spectra; 22(%) have flat, inverted, upturn, and complex spectral shapes, and 18(%) have peaked spectra (PS). The majority of the PS sources in the sample (20/31) are megahertz-peaked spectrum source candidates, i.e. possibly very young and compact radio galaxies. The median values of the variability indices at 11 and 5 GHz are (V_{S_{11}}=0.14) and (V_{S_{5}}=0.13), which generally indicates a weak or moderate character of the long-term variability of the studied galaxies. The typical radio luminosity and radio loudness are (L_{5}=10^{43}{-}10^{44}) erg s({}^{-1}) and (log R=3{-}4) respectively. We have found less prominent features of the bright compact radio cores in our sample compared to high-redshift quasars at (zgeq 3). The variety of the obtained radio properties shows the different conditions for the formation of radio emission sources in galaxies.

The development of methods for the radio frequency interference mitigation becomes a fundamental challenge for any radio astronomy research. In this paper, we report on the development and creation of a new spectrometer designed for solar observations at the RATAN-600 radio telescope, capable of excising radio interference using a statistical algorithm based on the spectral kurtosis estimation. The implementation of the external analog interface and the operation of the digital signal processing system based on the FPGA are described. The maximum spectral resolution reached is 122 kHz in the frequency band of 1.0–3.0 GHz. The output spectrum has from 64 to 8192 frequency bins, depending on the requirements of the observer, the output rate is 120 spectra per second. The test results and the first observations of the Sun show that the research method can successfully detect and suppress interference from most of the local radio interference sources.

This work is devoted to studying the influence of the bar on the orbital dynamics of globular clusters. The orbits of 45 globular clusters in the central galactic region with a radius of 3.5 kpc were analyzed using spectral dynamics methods in order to identify objects captured by the bar. To form the 6D phase space required for orbit integration, the most accurate astrometric data to date from the Gaia satellite (EDR3), as well as new refined average distances to globular clusters, were used. Since the parameters of the Milky Way bar are known with very great uncertainty, the orbits were constructed and their frequency analysis was carried out by varying the mass, length and angular velocity of rotation of the bar in a wide range of values with a fairly small step. The integration of orbits was carried out at 2.5 billion years ago. As a result, bar-supporting globular clusters were identified for each set of bar parameters. For the first time, an analytical expression has been obtained for the dependence of the dominant frequency (f_{X}) on the angular velocity of rotation of the bar. In addition, the probabilities of globular clusters being captured by the bar were determined when the bar parameters were varied in certain ranges of values according to a random distribution law. A list of 14 globular clusters with the most significant capture probabilities is given, with five GCs—NGC 6266, NGC 6569, Terzan 5, NGC 6522, NGC 6540—showing the probability of capture by the bar (Pgeq 0.2). A conclusion is made about the regularity of the orbits of globular clusters based on the calculation of approximations of the maximum characteristic Lyapunov exponents.

The lifetimes and length-scales for supergranular cells in active and quiescent regions of the solar chromosphere, and the relation between the two, were studied using a time series of Ca II K filtergrams. The lifetimes, in contrast to supergranular length scale and fractal dimension, show no significant dependence on solar latitude, suggesting that cell lifetimes are independent of the differential rotation and a possible supergranular super-rotation. The functional form of the relation was obtained guided by a comparison of the distributions of the two supergranular parameters. We infer a linear dependence of cell lifetime on area, which can be understood by the assumption of the network’s evolution via a diffusion of the magnetic field. Our analysis suggests that the diffusion rate in quiet regions is about 10(%) greater than in active regions.

We present an optical-to-radio study of the BL Lac objectS4 0954+658 observations during 1998–2023. The measurements wereobtained with the SAO RAS Zeiss-1000 and AS-500/2 0.5-m telescopesin 2003–2023, with the RATAN-600 radio telescope at 1.25 (0.96,1.1), 2.3, 4.7 (3.7, 3.9), 8.2 (7.7), 11.2, 22.3 (21.7) GHz in1998–2023, with the IAA RAS RT-32 Zelenchukskaya and Badarytelescopes at 5.05 and 8.63 GHz in 2020–2023, and with the RT-22single-dish telescope of CrAO RAS at 36.8 GHz in 2009–2023. Inthis period the blazar was showing extremely high broadbandactivity with the variability amplitude of the flux densities upto 70–100(%) both in the optical and radio domains. During theperiod of 2014–2023 the blazar displayed extremely high activityin the radio wavelengths, and we detected multiple radio flares ofvarying amplitude and duration. The large flares last on averagefrom 0.3 to 1 year at 22–36.8 GHz and slightly longer at5–11.2 GHz. The optical flares are shorter and last 7–50 days.The characteristic time scale (tau) of variation at 5–22 GHz isabout 100 days in the most active epoch of 2014–2023 and about1000 days for the state with lower activity in 2009–2014. Wefound a general correlation between the optical, radio, and(gamma)-ray flux variations, which suggesting that we observe thesame photon population from different emission regions. Weestimated the linear size of this region as 0.5–2 pc fordifferent conditions. A broadband radio spectrum with twocomponents of the S4 0954+658 jet was modeled using bothelectrons and protons as emitting particles. The results suggestthat the synchrotron radio waves in this AGN may be produced byrelativistic protons.

We have undertaken a search for satellites around edge-on galaxiesin the EGIPS catalog, which contains 16 551 objects withdeclinations above (-30^{circ}). We searched for systems with acentral galaxy dominating in brightness by at least(1^{textrm{m}}) compared to its companions. As a result, wediscovered 1097 candidate satellites around 764 EGIPS galaxieswith projected distances less than 500 kpc and a radial velocitydifference less than 300 km s({}^{-1}). Of these, 757 satellitesaround 547 central galaxies have radial velocity accuracies higherthan 20 km s({}^{-1}) and satisfy the gravitationally boundcondition. The ensemble of satellites is characterized by anaverage projected distance of 84 kpc and an average radialvelocity dispersion of 103 km s({}^{-1}). Treating smallsatellites as test particles moving on isotropic orbits aroundcentral EGIPS galaxies, we determined the projected (orbital)masses of the edge-on galaxies. Within the luminosity range of(1.3times 10^{10}) to (42times 10^{10}) (L_{odot}), the totalmass of the systems is well described by a linear dependence(log M_{p}propto 0.88logleftlangle L_{K}rightrangle_{textrm{g}})with an average total mass-to-(K)-band luminosity equalto ((17.5pm 0.8) M_{odot}/L_{odot}), which is typical fornearby spiral galaxies such as the Milky Way, M 31 and M 81.