Astrophysical Bulletin最新文献

Chandrasekhar’s (H)-function plays an important role in applied sciences, such as radiative transfer scattering theory. In this paper a numerical solution of the nonlinear integral equation for Chandrasekhar’s (H)-function and its first derivative has been derived. In addition, numerical results for the zeroth, first, and second moments of the (H)-function are obtained. We have arranged a compact formulation for the Gauss-shifted Legendre quadrature set and used it for numerical computation. It can be seen from the derivation of the equations and application of the numerical method explained in detail that the present method can be applied to other problems in applied sciences. Numerical results consistent with those available in the literature have been obtained even in low-order approximations. Accordance between them corresponds to a difference of about 0.01(%). This explicitly illustrates the accuracy and capability of the method.

In this work, we present the program MOLLId (MOLecular Line Identification) for automated molecular line approximation with a Gaussian profile. Molecular identification was performed using multi-level comparison of the lines’ center frequencies and rest frequencies from the spectroscopic database. The program was tested in the identification of molecular lines in observed spectra of young stellar objects RCW 120 YSO S1 and RCW 120 YSO S2 located near the border of the RCW 120 PDR. In the spectra of the RCW 120 YSO S1 source, 100 lines of 41 molecules were identified over the level of 4–6 (sigma). In the spectra of the RCW 120 YSO S2 source, 407 lines of 79 molecules were identified over the 3–5 (sigma) level. Using the Intel Core i7-12700K CPU, identification time is equal to 6 and 8 minutes per spectral range for the YSOs S1 and S2, respectively. From the analysis of CH({}_{3})OH, CH({}_{3})CN, CH({}_{3})CCH molecules identified in RCW 120 YSO S2, we found a two-component structure and estimated the physical parameters in the LTE approximation for each of the components.

The paper presents methods for analyzing multiwavelength light curves of active galactic nuclei with uneven time sampling, including the use of the structure functions, autocorrelation and cross-correlation functions, Lomb–Scargle periodograms, and weighted wavelet analysis. The structure functions allow quantitative estimation of the temporal scales of variations, correlation functions provide detection of temporal delays between different frequencies, Lomb–Scargle periodograms detect periodicities in nonuniform data, and wavelet analysis makes it possible to localize variable processes in time and to study the evolution of the signal frequency composition. The comprehensive use of these methods allows detailed investigation of the temporal and frequency structure of physical processes in active galactic nuclei, taking into account the influence of the unevenness of experimental data. The advantages and limitations of each method are considered using examples of analyzing specific sources, and their practical significance for studying the variability of active galactic nuclei is demonstrated.

A method is proposed for constructing averaged phase curves of asteroid brightness for various taxonomic types. The method is based on a large number of astrometric observations published in the Minor Planet Center catalog, for which the apparent visual magnitudes of asteroids were measured simultaneously. Thousands of asteroids of each taxonomic type S, C, E, V, Q, L, D, and X were selected, and numerical integration of the equations of motion was performed. In the course of integration, for each observation, the component of the apparent magnitude dependent on the phase angle was determined. For asteroids of a given type, all obtained values were averaged over the phase angle. As a result, averaged phase curves characterizing each taxonomic type were constructed. The large volume of observational data makes it possible to clearly reveal the character of the opposition effect for different types. A shift of the phase curves with respect to zero at a zero phase angle was noted. This shift depends on asteroid size and differs among taxonomic types. The presence of such a shift indicates a systematic error in the absolute magnitudes of asteroids published in the Minor Planet Center catalog.

The atlas of the spectrum of the B[e] star CI Cam obtained with the 6-m BTA telescope of the SAO RAS applying the NES spectrograph in the wavelength range of 395–780 nm with a resolution of (lambda/Deltalambdageq 60,000) is presented. The atlas identifies about 400 spectral features and illustrates the diversity of spectral features of the unique star, forming in a complex circumstellar environment. The spectrum is dominated by forceful single-peaked H I, He I emissions and numerous double-peaked permitted and forbidden emission lines of ions of chemical elements starting from the CNO triad up to metals (Mg, Al, Ti, V, Cr, Fe) with ‘‘rectangular’’ profiles. The Fe II and [Fe II] emissions predominate in the spectrum. However, several double-peaked forbidden ion emissions were also detected: [V II], [Cr II], [Ni II]. The atlas is presented graphically, with a separate figure corresponding to each échelle order. A list of identified lines, including a number of known interstellar features is presented in table form. The supergiant status of CI Cam is confirmed by the richness of its spectrum with different features of nitrogen.

The article presents the results of the analysis of optical light curves of the massive binary system WR 20a (WN 6ha (+) WN 6ha). The analysis was performed with a binary system model, extending the standard Roche model for the case when both components of the system have powerful stellar winds. The model takes into account the collision of the winds and the influence of orbital motion on the collision zone. The observational light curves in (BVI) filters were taken from previously published papers, in which they were analyzed using the standard Roche model. The main difference between the results of our work and the previous results is that in our model the radii of the components are about 25(%) smaller. As a consequence, the luminosity of the system in our model decreased by approximately 40(%), and the distance to the system by 20(%). In addition, the model was able to successfully describe the observed asymmetry of the light curve with respect to the phases of the conjunctions, which is impossible in the standard Roche model. The model light curves were also compared with the observational curves obtained by the TESS satellite and the ASAS-SN project. It was shown that, taking into account recent studies of interstellar extinction in the direction of the young open cluster Westerlund 2, the distance to WR 20a obtained in our calculations is consistent with the hypothesis that WR 20a is a member of the cluster.

The paper presents spectropolarimetric monitoring of three chemically peculiar stars, HD 13404, HD 225114, and BD ({+}64^{circ}) 325, whose peculiarity has been discovered during the SDSS/APOGEE IR survey. Observations were carried out with the 6-m BTA telescope equipped with a circular polarization analyzer. For the first time, the longitudinal magnetic field phase curves were constructed for these stars, and their rotational periods were refined using the TESS photometry. Significant differences in the nature of their magnetic variability were discovered: HD 13404 shows a weak modulation, probably due to the observation geometry, while HD 225114 and BD ({+}64^{circ}) 325 were revealed to have a complex magnetic field topology associated with the non-uniform surface chemical distributions.

The main objectives of this work is to obtain the average magnetic phase curves of stars in order to determine their parameters for the purpose of describing their magnetic behavior and for statistical studies. This work was necessitated by two factors: the appearance of new high-accuracy magnetic measurements, which made it possible to refine the variability parameters for some previously studied stars; and the availability of new magnetic measurements for stars with rotation periods determined from high-accuracy photometry from space missions. As a result of this addition, average magnetic phase curves are currently available for 415 stars, 258 of which are Ap/Bp stars. Such a large number of Ap/Bp stars allows one not only to estimate the variability parameters but also to try to find a cause explaining the extremely slow rotation of some of these stars.

Based on the analysis of the long-term light curve of the young binary system DF Tau spanning approximately 125 years, we infer that its brightness variations are associated with changes in the accretion rate from the circumstellar protoplanetary disk onto the primary star. We have also substantially improved the orbital parameters of DF Tau, which enables us to align its secular light curve with the evolution of the binary’s component separation. The relationship between the long-term brightness variations and the orbital motion of DF Tau, if present, appears to be inconsistent with theoretical predictions. Notably, similar discrepancies between theory and observations are also seen in other young binary systems. Furthermore, the source of the polarized radiation in the optical range is found to be located at a distance of (0overset{primeprime}{.}5) from the star, with the polarization variability showing no dependence on the orbital phase.

In this paper, we continue our research on constructing the optimal fundamental plane (FP) of galaxy groups and clusters for measuring their distances. This work was carried out using archival data from the SDSS and 2MASX catalogs. We present the fundamental planes (scaling relations of dynamical and photometric parameters) of 205 galaxy groups and clusters ((z<0.15)). We found that in the near infrared ((K)-filter), the distribution of galaxy clusters is well approximated by three-parameter planes of the form (R_{e}proptosigma^{1.01pm 0.05}langle I_{e}rangle{{}^{-0.32pm 0.03}}) and (R_{e}propto N^{0.43pm 0.01}langle I_{e}rangle^{-0.40pm 0.02}) and a four-parameter plane of the form (R_{e}proptosigma^{0.15pm 0.06}langle I_{e}rangle^{-0.39pm 0.02}N^{0.38pm 0.02}). The fundamental planes have logarithmic standard deviations of 0.060, 0.036, and 0.035. If we use the fundamental planes to measure distances of galaxy systems, these deviations correspond to 14(%) and 8(%) errors in the distance of a single cluster. Using the four-parameter fundamental plane, we obtained the scatter of the Hubble constant (H_{0}=70pm 5.6text{ km s}^{-1}) Mpc({}^{-1}). Using three fundamental planes of galaxy clusters, it was found that the velocity of the average drift motion in the three-degree cosmic microwave background (CMB) system of five superclusters of galaxies from the SDSS region is (langle V_{textrm{pec}}rangle={+}241pm 180text{ km s}^{-1}).