Astronomy Reports最新文献

Massive stars play an important role in the Universe. Unlike low-mass stars, the formation of these objects located at great distances is still unclear. It is expected to be governed by some combination of self-gravity, turbulence, and magnetic fields. Our aim is to study the chemical and physical conditions of dense clumps at different evolutionary stages. We performed observations towards 5 regions of massive star and stellar cluster formation (L1287, S187, S231, DR 21(OH), NGC 7538) with the IRAM-30m telescope. We covered the 2 and 3–4 mm wavelength bands and analyzed the lines of HCN, HNC, HCO⁺, HC₃N, HNCO, OCS, CS, SiO, SO₂, and SO. Using astrodendro algorithm on the 850 µm dust emission data from the SCUBA Legacy catalog, we determined the masses, H₂ column densities, and sizes of the clumps. Furthermore, the kinetic temperatures, molecular abundances, and dynamical state were obtained. The Red Midcourse Space Experiment Source survey (RMS) was used to determine the clump types. A total of 20 clumps were identified. Three clumps were found to be associated with the H II regions, 10 with young stellar objects (YSOs), and 7 with submillimeter emission. The clumps have typical sizes of about 0.2 pc and masses ranging from 1 to 10²({{M}_{ odot }}), kinetic temperatures ranging from 20 to 40 K and line widths of H¹³CO⁺ (1–0) approximately 2 km s^–1. We found no significant correlation in the “line width–size” and the “line width–mass” relationships. However, a strong correlation is observed in “mass–size” relationships. The virial analysis indicated that three clumps are gravitationally bound. Furthermore, we suggested that significant magnetic fields of about 1 mG provide additional support for clump stability. The molecular abundances (relative to H₂) are approximately 10^–10–10^–8.

Pulsar B1642–03 has been observed with the Radioastron ground-space interferometer during the implementation of the Key Science Program of the project. Observations were made on September 8, 2013, in the 92-cm band at frequencies 316–332 MHz. The Westerbork Synthesis RT (WSRT) has been used as a ground arm of the interferometer. The baseline projections of the interferometer have changed during the observations approximately from 10 000 to 20 000 km, and the positional angle of the baseline has changed almost for 50°. This configuration has made it possible to estimate the angular diameter of the scattering disk in different positional angles. It has been found that the shape of the scattering disk can be presented in the form of an ellipse with an axial ratio of 2 : 1. Comparison of the angular size of the scattering disk and the delay time of scattered rays has indicated a possible irregular structure of the scattering disk, which may be due to lensing of radio waves when passing through the Stromgren zone near star (zeta ) Oph.

This study considers the framework of a planar Restricted Three-Body Problem (RTBP) in which both the primaries are oblate spheroids with their equatorial planes coincident with the plane of motion while the more massive primary is a source of radiation. The nonlinear stability of the triangular equilibrium points is investigated with the help of the mean motion derived by Sharma et al. [15] which is more accurate than the one used in earlier works. The Lagrangian of a third infinitesimally small body when it is near either of the triangular equilibrium points L₄/L₅ is formulated with respect to a synodic coordinate frame located at the respective equilibrium point. From the second order part of the Lagrangian, extracted using Taylor series expansion, second order part of the Hamiltonian of the system is derived and the equations of motion of the third body near the equilibrium points are obtained. Analyzing the characteristic equation of the system, which is similar for both the equilibrium points L₄/L₅, critical mass value that marks the linear stability of the triangular equilibrium points is obtained. Furthermore, Moser’s conditions are employed to find the two exceptional values of the mass parameter in the stable range at which stability cannot be guaranteed. By comparing with the results available in the literature, all three critical mass values are found to be lower than the values obtained for an ideal RTBP framework without oblateness or photo-gravitational effect. In addition to that, critical mass values are also affected due to change in the mean motion expression.

In this paper, the theoretical and observational problems of the search for cosmic strings (CS) by methods of modern astrophysics are discussed and new possibilities for further observational search for CS are proposed and justified. In recent works by the authors, it was shown for the first time that taking into account the geometry of the CS (tilt and bend) cardinally affects one of the main observational methods of searching for CS: searching for chains of images of galaxies that should be formed due to the effect of gravitational lensing of background galaxies on the CS. Further, these theoretical developments were applied to the analysis of observational data of the double galaxy SDSS J110429.61+233150.3, previously found in the field of the assumed CS (CSc-1), identified, in turn, by the analysis of the CMB anisotropy. Based on these long-term studies, this paper for the first time identifies the fundamental problems of approximate theoretical models, within which the evolution of both CS networks and single CS is traditionally considered, and also for the first time justifies the rejection of the traditional search for extended chains of gravitational-lens pairs. In this paper, a new detailed strategy for searching for CS is proposed by identifying and analyzing the characteristic clustering of gravitationally lensed pairs. This strategy is demonstrated by the analysis of gravitationally lensed pairs in the CSc-1 region, and the requirements for future observations are indicated. Arguments are also given that admit a change in the linear density of CS in a wide range and that “heavy” CS do not contradict modern observational data, including that on the CMB anisotropy and the gravitational-wave background. A strategy for the systematic analysis of binary quasars (having a gravitationally lensed nature and an unidentified lensed object) as lensed on CS is discussed.

In the framework of photogravitational axisymmetric restricted five-body problem (PAR5BP), the existence and stability of the in-plane equilibrium points, the possible regions for motion are explored and analyzed numerically along with good agreement of the graphical results. We have determined the dynamics of the infinitesimal mass in the PAR5BP. We have determined the locations of the libration points (LPs) in the convex configuration. Further, the parametric evolution of the equilibrium points as the function of radiation parameter has been shown. The stability along with the zero velocity surface associated with the libration points are also investigated. It has been observed that none of the libration point is stable for any value of considered parameters.

The infrared (IR) to X-ray luminosity ratio (IRX) is an indicator of the role of the dust plays in cooling of hot gas in supernova remnants (SNRs). Using the 3D dynamics of gas and interstellar polydisperse dust grains we analyzed the evolution of SNR in the inhomogeneous medium. We obtained spatial distributions of the surface brightness both of the X-ray emission from hot gas inside SNR and the IR emission from the SNR swept-up shell, as well as, the average gas temperature in the SNR, ({{T}_{{text{X}}}}). We found that the IRX changes significantly (~3–30 times) as a function of impact distance within the SNR and its age. In a low inhomogeneous medium the IRX drops rapidly during the SNR evolution. On the other hand, if large inhomogeneities are present in the medium, the IRX is maintained at higher levels during the late SNR evolution at radiative phase due to replenishment of the dust in the hot gas from incompletely destroyed fragments behind the shock front. We showed that the SNR evolution in terms of the {({{T}_{{text{X}}}}-{text{IRX}})} diagram is determined by the onset of the radiative phase. We illustrated that decreasing gas metallicity or density leads to high values of temperature and IRX ratio. We discuss how our results can be applied to the observational data to analyse the SNR older than 10 kyr (i.e., when the mass of the swept-up dust in the shell is expected to exceed that produced in the SNR) in the Galaxy and Large Magellanic Cloud.

In this paper, the results of complex numerical modeling of the transit absorptions of hot exoplanet WASP-69b in the metastable helium HeI(2³S) line have been presented. The modeling has been provided using a 3D MHD code, which allows for the simulation of effects that influence the absorption profile in various spectral lines and predicts a realistic distribution of the density of the main components and the structure of the interacting flows of planetary and stellar material. It has been shown that the simulated transit absorption profiles closely match the height and width of the measured transit profiles, which allowed for the estimation of the physicochemical parameters in the area of exoplanet WASP-69b.

The problem of space debris becomes an important obstacle to human expansion into space. The paper presents a classification of space debris objects, describes the population of near-earth orbits, as well as methods for monitoring space debris and ways to combat it.

The paper describes less obvious types of space hazards, such as encounters of the Solar System with other stars, crossing of the Galactic plane, passage through a molecular cloud, nearby supernova explosions, and gamma-ray bursts.

The paper describes major aspects of space weather and their influence on Earth and humankind.