Astrophysical Bulletin最新文献

The kinematics of the young stellar association near the Sun TW Hya is studied. Kinematic estimates of the age of this association were obtained in two ways. The first method—the analysis of stellar trajectories integrated back in time—gave an estimate of the age (t=4.9pm 1.2) Myr. The second was to analyze the instantaneous velocities of the stars; it showed that there was a volume expansion of the stellar system with the angular velocity coefficient (K_{xyz}=103pm 12) km s({}^{-1}) kpc({}^{-1}). Based on this effect, the time that passed from the beginning of the expansion of the TW Hya association to the present moment was found, (t=9.5pm 1.1) Myr. The following principal semi-axes of the residual velocity ellipsoid were determined: (sigma_{1,2,3}=(5.25,1.84,0.35)pm(0.34,0.63,0.26)) km s({}^{-1}).

The stellar and integral photometry of 30 irregular dwarf galaxies was performed in the (F606W) ((V)) and (F814W) ((I)) filters based on archival images from the Hubble Space Telescope. Distances were determined for 12 galaxies using the TRGB method. Branches of blue supergiants were identified on the plotted Hertzsprung–Russell diagrams, and the average luminosities of the three brightest stars were calculated. The color indices ((V-I)) and luminosities of galaxies in the (V) and (I) filters were determined in circular apertures with the maximum radius (textrm{Rad}=50^{primeprime}). A diagram of the dependence between the luminosities of galaxies and their brightest stars was developed, which shows that the luminosity of the brightest stars increases with increasing luminosity of the parent galaxies. A comparison of the dependence for 30 irregular galaxies with a similar one for 150 spiral and irregular galaxies, published by Tikhonov et al. in 2021, shows their similarity. This result confirms the hypothesis that the absence of bright massive stars in dwarf irregular galaxies cannot be explained by the small number of stars in these galaxies. Using the results of Hunter et al. (2019 and 2021), we developed a dependence between the luminosity of galaxies and the mass of the third-largest H I cloud of these galaxies. The presented correlation, as well as the well-known Larson correlation proposed in 1982, between the mass of molecular hydrogen clouds and the mass of stars born in them, give us reason to conclude that the dependence between the luminosity of galaxies and the brightest stars is a consequence of the correlation between the luminosity (mass) of galaxies and the average mass of the gaseous clouds of these galaxies.

The linear polarization observations of S5 0716(+)714 carried out by the author in 2019–2021 were continued from December 8, 2021 to March 12, 2022. These observations confirm the author’s statment made in 2022 about a periodic dependence of the degree of linear polarization of S5 0716(+)714 on its optical flux. The harmonic period varies from 3 to 8 mJy in the 3 to 55 mJy interval.

We present the results of a spectral survey towards a dense molecular condensation and young stellar objects (YSOs) projected on the border of the H II region RCW 120 and discuss the emission of the 20 molecules that produce the brightest lines. The survey is performed with the APEX telescope in the 200–260 GHz frequency range. We provide evidences for two outflows in the dense gas. The first one is powered by the RCW 120 S2 YSO and oriented along the line of sight. The second outflow around RCW 120 S1 is aligned almost perpendicular to the line of sight. We show that the areas with bright emission of CH({}_{3})OH, CH({}_{3})CCH and CH({}_{3})CN are organised into an onion-like structure, where CH({}_{3})CN traces warmer regions around the YSOs than the other molecules. Methanol seems to be released into the gas phase by shock waves in the vicinity of the outflows while thermal evaporation still does not work towards the YSOs. We find only a single manifestation of the UV radiation in the molecules, namely, enhanced abundances of small hydrocarbons CCH and c-C({}_{3})H({}_{2}) in the photo-dissociation region.

Using stellar evolution models, empirical atlases of stellar spectra, the ATLAS9 stellar model library, and published relations between observational and astrophysical characteristics of stars of different luminosity classes, we investigate the possibilities of their separation in the space of atmospheric and photometric parameters (T_{textrm{eff}}{-}log g), (T_{textrm{eff}}{-}(B-R)_{0}) (Johnson), (T_{textrm{eff}}{-}(BP-RP)_{0}) (Gaia). We propose an approximation of the zero age (ZAMS) and terminal age (TAMS) main sequence lines in the (T_{textrm{eff}}{-}log g) coordinates, and show that more than (90%) of stars of luminosity class III from empirical atlases of stellar spectra are shifted toward smaller values of (log g) relative to TAMS and, as a rule, have values of (log g<3.2). It is shown that the (T_{textrm{eff}}{-}(B-R)_{0}) dependence in the Johnson photometric system is sensitive to the luminosity class in certain ranges of effective temperatures. At the same time, the (T_{textrm{eff}}{-}(BP-RP)_{0}) dependence for main-sequence stars in the Gaia photometric system is found to be valid with an accuracy better than (0overset{textrm{m}}{.}15) for stars of all luminosity classes and all spectral types earlier than M2.

Observations of quasars show that the polarization position angle of the emission coming from them varies greatly over time, including periods called rotations during which the angle changes in an orderly manner. The study proposes a method for identifying such events and assessing their statistical significance. The operation of the method is demonstrated using the example of long-term polarimetric observations of the blazars CTA 102, 3C 454.3, and OT 081. During the analysis of light curves, 51 rotations of the polarization position angle were found and it was shown that for CTA 102 and 3C 454.3 the rotations are predominantly oriented in one direction.

Comparison of the properties of magnetic O stars with He-strong objects showed their family connection; the mechanism of their formation and further evolution is obviously the same. The family of magnetic O stars continues the sequence of known magnetic Ap objects towards higher masses. The observed differences in properties are associated with the large mass of O objects.

The results of studying manifestations of activity of the K8V dwarf FR Cnc according to the data from the TESS space telescope archive and other literary sources are presented. The TESS mission archive contains the results of observations of FR Cnc in three sectors: 44, 45, and 46 of a total duration of 78.3 days. The light curves of the star are characterized by the variability due to rotational modulation caused by the presence of cool spots on the surface. Based on the combined data from three observation sectors, the value of the star’s rotation period was estimated as (P_{rm{rot}}=0.8257) days. Features of the amplitude changes of the stellar brightness variability, the shape of the phase light curve, and the position of the minima are highlighted. The fraction of the surface of FR Cnc occupied by spots varied in the range of 8.7–11.4(%) of the visible surface area of the star. The FR Cnc light curves are characterized by a large number of flares of different amplitudes. One of the flares is considered as an example; according to the estimate, its energy is (E_{textrm{TESS}}=1.9times 10^{34}) erg. To determine the long-term activity cycles of the star FR Cnc, the data from the Digital Access to a Sky Century @ Harvard (DASCH) project were used for the observation interval from 1886 to 1989 lasting 103 years in the photographic system close to the photometric one in the (B) filter. An independent estimate of (P_{textrm{cycl}}) was made using the data from the long-term Kamogata Wide-field Survey (KWS) in the (V) filter. Analysis of the data from these surveys showed the long-term brightness variability of FR Cnc with a characteristic time of the order of 4500–4600 days (12.3–12.6 years).

This paper presents a method for estimating precipitable water vapor from radiometric data using machine learning methods. The results of a study of precipitated water vapor for the territory of Chirag (Dagestan), Terskol peak (Elbrus region), Badary observatory (Buryatia) and the Spitsbergen archipelago are presented. A comparative analysis of the assessment of precipitable water vapor for the territory of ‘‘Badary’’ was carried out using GNSS, MERRA-2, water vapor radiometer data and predicting values using machine learning methods based on data from the MIAP-2 microwave radiometer.

The results of photometric, polarimetric, and spectroscopic observations of the young star ZZ Tau IRS in the visible and near-infrared bands are presented. Against the continuum of an M spectral type star about 50 emission lines of allowed (H I, He I, Na I, S II) and forbidden (O I, O II, O III, N I, N II, S II, Ca II, Fe II, Ni II) transitions were identified. It was found that from the autumn of 2020 to the beginning of 2023, the brightness of the star in the visible region decreased ((Delta Iapprox 1overset{textrm{m}}{.}5)) and then began to return to the initial level. As the visible brightness of the star declined, its color indices decreased in the visible region, but increased in the near-IR bands. At light minimum, the degree of polarization in the (I) band reached approx 13(%), and the equivalent widths of, e.g., the H(alpha) and [S II] (lambda) 6731 lines increased to 376 and 79 ({{text{AA}}^{circ}}), respectively. Arguments are given in favor of ZZ Tau IRS being a UX Ori type star, and its variability being due to eclipses by dust clouds, which are inhomogeneities in the dusty disk wind. Forbidden lines are formed both in the disk wind and in the jet, the axis of what is oriented along (PA=61^{circ}pm 3^{circ}). The jet mass-loss rate exceeds (5times 10^{-10}M_{odot}) yr({}^{-1}), what is abnormally large for a star with a mass less than (0.3M_{odot}). Apparently, the disk wind of ZZ Tau IRS is not axially symmetric, probably due to the azimuthal asymmetry of the protoplanetary disk found earlier from ALMA observations.