Astrophysical Bulletin最新文献

Four samples of open star clusters (OSCs) with average ages of 5.2, 18.6, 40, and 61 Myr have been analyzed. The selection of these OSCs was carried out from a narrow region inclined to the Galactic (Y) axis at an angle of (25^{circ}). Spectral analysis of the vertical positions and velocities of the selected clusters showed that the Radcliffe wave is associated with OSCs no older than 30 Myr. The following estimates of the Radcliffe wave characteristics were obtained for the OSCs with an average age of 5.2 Myr: (z_{textrm{max}}=117pm 12) pc with the wavelength (lambda=4.55pm 0.14) kpc, and the vertical velocity disturbance amplitude (W_{textrm{max}}=4.86pm 0.19) km s({}^{-1}) with the wavelength (lambda=1.74pm 0.08) kpc. For the OSCs with an average age of 18.6 Myr, the estimates are as follows: (z_{textrm{max}}=54pm 5) pc and (lambda=6.30pm 0.12) kpc, and the vertical velocity disturbance amplitude (W_{textrm{max}}=7.90pm 0.16) km s({}^{-1}) and (lambda=0.83pm 0.11) kpc. The radial motion of the Radcliffe wave away from the Galactic center has been confirmed. The velocity of such movement is 10 pc Myr({}^{-1}). In our opinion, the spatial distribution of OSCs younger than 30 Myr does not contradict the hypothesis of the association of the Radcliffe wave with the impact of shock waves from supernova explosions that arose on an extended front comparable in scale to the entire wave, that is, about 2 kpc in size.

We have constructed and analyzed the secular light curve of BP Tau, a classical T Tau star. Wave-like variations in the average brightness level of the star with an amplitude of (Delta Bapprox 0overset{textrm{m}}{.}2) and a characteristic time of several decades were found. We present arguments in favor of the concept that three deep ((Delta Bsim 1overset{textrm{m}}{.}5)) dimming episodes lasting from one hour to several days are associated with the eclipse of a hot (accretion) spot by the dust infalling on the star along with gas. It is possible that such eclipses, albeit with a smaller amplitude, are the reason for the lack in BP Tau of a strictly expressed brightness variation periodicity related to axial rotation. We found that in the distance range of 0.1 to 200 AU, BP Tau has no companions with masses greater than (0.2;M_{odot}). Possible reasons of brightness and color index variability of the star on different time scales are discussed.

A revision of the orbital parameters of the spectroscopic binary Cepheid TX Del, often classified as a BL Her subtype of T2 variables, has been carried out. The pulsation radius is determined from two series of photometric observations, including Gaia DR3: (langle Rrangleapprox 22.4pm 0.8,R_{odot}) for the ((B,V)) bands and (langle Rrangleapprox 20.6pm 0.6,R_{odot}) for the ((BP,RP)) bands, respectively. The amplitude of the radius variations is about (2,R_{odot}). The new radius estimates are significantly smaller than the previous estimates, which were in the range of 37 to 60 (R_{odot}). Using the Bayesian distance, (langle Drangleapprox 1064pm 25) pc, the absolute values of TX Del are estimated to be (langle M_{V}rangle_{I}approx{-}1.31pm 0.04) mag and (langle M_{G}rangle_{I}approx{-}1.40pm 0.03) mag, respectively. The absolute magnitude and mean radius of TX Del are in excellent agreement with the predictions of the ‘‘period–luminosity’’ and ‘‘period–radius’’ relations for T2 Cepheids with a period of (P_{textrm{pls}}approx 6.1662) days; TX Del is approximately (2overset{textrm{m}}{.}2) fainter than classical Cepheids with the same period. It is shown that for orbital plane inclination angles (20^{circ}<i<(30{-}35)^{circ}) the satellite can be more massive than the main component, which leads to an evolutionary scenario with mass exchange. The current Roche sphere filling degree is (37{-}55%). The orbit of the binary system TX Del calculated based on astrometric data from Gaia DR3 and radial velocity is limited by a (|z|<0.42) kpc torus with the inner and outer radii equal to 7.2 and 8.3 kpc, respectively, while the vertical velocity is (|V_{z}|leq 38) km s({}^{-1}); the period of galactovertical oscillations is about 77 Myrs. The tangential velocity is 220–255 km s({}^{-1}). The high metallicity and kinematic characteristics allow us to refer TX Del to the population of the old disk of the Milky Way with a vertical scale (H_{z}approx 0.3) kpc (or to a thick disk with (H_{z}approx 0.85) kpc). At the same time, in terms of pulsation characteristics (period, luminosity, and position in the instability strip), TX Del is close to Population II Cepheids with (textrm{[Fe/H]}<{-}1) (including globular cluster Cepheids) that are at the evolutionary stage after the horizontal branch. To finally clarify the evolutionary status of such variables, additional evolutionary and pulsation calculations are required over a wider range of periods and luminosities.

We study the formation of the Hercules stream in the model Galactic disk which includes the outer resonance ring (R_{1}R_{2}) located near the Outer Lindblad Resonance (OLR) of the bar. The Hercules region and the anti-Hercules region, introduced for calibration, were restricted in space by the solar neighbourhood (r<0.5) kpc, and on the ((V_{R}), (V_{T})) plane by ellipses centered at (V_{R}=25) km s({}^{-1}) and (V_{T}=200) km s({}^{-1}) (Hercules), and at (V_{R}=-25) km s({}^{-1}) and (V_{T}=200) km s({}^{-1}) (anti-Hercules). The number of stars in the Hercules region reaches a maximum in the time period of (2-3) Gyr from the start of simulation and the number of stars in the anti-Hercules region oscillates with a period of (1.8pm 0.1) Gyr. The majority of stars in the model disk located in the Hercules and anti-Hercules regions have orbits elongated perpendicular and parallel to the bar, respectively. The median value of the initial distances of stars in the Hercules (anti-Hercules) region is slightly smaller (larger) than the OLR radius, respectively. There are two types of orbits in the Hercules region. Orbits of the first type always lie inside a figure bounded by two ellipses elongated perpendicular to the bar. Orbits of the second type are elongated at the angles of (-60^{circ}) or (60^{circ}) to the major axis of the bar most of the time. The distribution of stars in the Hercules region along the period of slow oscillations in the angular momentum has two maxima: (P=0.7) and 2.6 Gyr corresponding to orbits of the first and second type. In the anti-Hercules region, most orbits are captured by libration relative to the major axis of the bar with a period of 1.9 Gyr. In general, orbits in the Hercules and anti-Hercules regions support the outer rings (R_{1}) and (R_{2}) elongated perpendicular and parallel to the bar, respectively. Stars from the Gaia DR3 catalog located in the Hercules region appear to be, on average, brighter, bluer, and more luminous than stars in the anti-Hercules region which is probably caused by selection effects due to different distributions of these stellar samples over the Galactic latitude (b).

In this paper we discuss the problems of classification of globular cluster systems (GCS), in particular, the problem of the auxiliary parameter. The simplest methods of their classification are proposed. The possibilities of classification by the degree of concentration of GCS to the center of the galaxy and the use of the velocity anisotropy parameter are studied. Empirical relationships between the initial value of the virial parameter and the physical characteristics of GCSs are found. It is shown that GCSs can be classified using the initial value of the virial parameter.

In this paper, we study the distribution law of the random force modulus in the nearest neighbor approximation (generalized Holtsmark distribution) and the asymptotic behavior of the Holtsmark distribution for large random forces for a fractal stellar medium in the solar neighborhood. The role of collisional processes and random forces in the dynamics of stellar systems is considered. This study is based on the investigation of the spatial distribution of 200 000 stars of all spectral classes at distances from 1 to 100 pc from the Sun according to Gaia DR2 data, the results of which indicate the presence of fractal structures in the solar neighborhood with a fractal dimension of (Dsimeq 2.41). The asymptotic distribution of random force derived for a fractal stellar medium demonstrates the important role of strong fields, with the magnitude of the random force decreasing somewhat more slowly compared to its distribution for a homogeneous medium.

The structure of the magnetic field of HD 37479 corresponds to the structure of a dipole displaced along the axis by a significant value (Delta a=0.2R_{*}) and across the axis by the value (Delta a=0.05R_{*}). As a result, the magnetic field is distributed extremely unevenly over the stellar surface. The maximum values of the average surface magnetic field are equal to (B_{s}=+2591) and (-7486) G. It is in these areas that the maximum wind occurs, and also in approximately these same areas the maximum helium abundance is observed. A cloud of rarefied gas extends along the magnetic equator, in which H(alpha) emission lines are formed.

The study presents both photometric and kinematic Gaia DR3 analyses of the nonrelaxed open cluster Stock 3, which is found to be located at a distance of (2.95pm 0.70) kpc and to have an age of (16pm 4) Myr. We analyze the data to infer the cluster membership and thus determine the total mass, initial mass function, and the dynamical and kinematical status.

In this paper, we describe the design and technical features of the Rayleigh laser guide star (LGS) system as a reference source of the adaptive optics system (AOS) intended for use at the Zeiss-2000 telescope of the Terskol Peak Astronomical Observatory (coordinates (43overset{circ}{.}27631) N, (42overset{circ}{.}49939) E) located at an altitude of 3150 m above sea level. Experimental testing of the Rayleigh LGS system at the Zeiss-2000 telescope was carried out. The presented numerical estimates of the correlation radius (r_{0}) show that in the future, the use of an AOS with a Rayleigh LGS at this telescope will improve the quality of the formed image by an order of magnitude.

The paper is aimed at studying the variability of the Be star (omega) Ori. We analyzed the optical spectra of the star taken with the 2.5-m SAI25 telescope of the Caucasus Mountain Observatory (CMO) of SAI MSU. A rapid variability of the H and He line profiles with periods from 37 to 150 minutes are revealed. The photometric light curves of (omega) Ori obtained with the TESS satellite regular brightness variations with periods of 0.94 and 1.86 days have been detected. We also discuss X-ray observations and search for a magnetic field of (omega) Ori.