Astronomy Reports最新文献

We present the study of gradient profiles of the Vela Jr. northwestern rim in X-ray emission and the morphology of this supernova remnant in various spectral ranges of electromagnetic radiation to estimate the distance to the object and its age. This work involves radiation intensity spatial distributions for the northwestern rim of the supernova remnant RX J0852.0–4622 in the X-ray energy range, 1000.0–2000.0 eV, obtained from measurements of the EPIC-pn camera of the XMM-Newton space observatory for four consecutive time intervals. From the calculated shifts over the period from 2004 to 2018 of the X-ray intensity profiles along the northwestern rim of Vela Jr., limits were obtained on the angular expansion rate of the shock wave of this remnant’s region into a cloud of gas, probably hydrogen: minimum speed (V_{theta }^{{{text{max}}}}) = 0.29('' ) ± 0.04('' ) year^–1 and maximum (V_{theta }^{{60}}) = 0.82('' ) ± 0.11('' ) year^–1. The hydrogen cloud with which the supernova shock wave interacts along the northwestern rim of Vela Jr. is very inhomogeneous. The upper limits for the age of the remnant and the distance to it based on the cloud density estimate are 1920 years and 450 pc, respectively. More stringent restrictions on such parameters of RX J0852.0–4622 as its age and distance to it were obtained by analyzing the remnant’s two-ring morphology based on its images in ultraviolet, X-ray, radio and gamma rays: 1190 ± 250 years and 280 ± 60 pc.

Nitric oxide is a potential biomarker in the N₂–O₂ atmospheres of terrestrial exoplanets, which can be detected by space missions, including the planned launch of the Russian Spektr-UV observatory. From observations of the Earth’s thermosphere in the polar regions, it is known that important sources of formation of this molecule are the precipitation of high-energy electrons into the planet’s atmosphere, as well as the non-thermal processes accompanying them. In this paper, we study the non-thermal processes of nitric oxide formation in the polar regions of the Earth’s upper atmosphere, as well as the atmospheres of exoplanets located in the potential habitable zone of active stars. For this purpose the following models are developed: a numerical kinetic Monte Carlo model of the interaction of energetic electrons with atmospheric gas, a kinetic Monte Carlo model of the interaction of suprathermal N(⁴S) atoms formed as a result of dissociation of N₂ molecules by electron impact with the surrounding gas; a model of odd nitrogen chemistry with molecular and eddy diffusion. Based on results of calculations, it is confirmed that the process of dissociation of N₂ by an electron impact during the interaction of the stellar wind with the atmosphere of the planet is an important source of suprathermal N atoms, which contribute to a significant increase in the non-thermal formation of NO in the N₂–O₂ atmospheres of terrestrial planets (both locally, in the case of a planet’s own magnetic field, and throughout the whole planet’s surface, in case of its absence). Since the column concentration of NO during flares becomes larger, therefore, the chances of detecting of nitric oxide biomarker in the atmospheres of the terrestrial-type exoplanets located in the potential habitable zone of active stars are also become larger.

Variations in the radiation intensity of pulsar B0950+08 from 2014 to 2022 with scales from minutes to years were analyzed. The observations were obtained in daily survey using the Large Phased Array (LPA) radio telescope. The high variability of radiation is shown both from pulse to pulse and on scales greater than 3 min. The average value of the estimated amplitude of these variations in 3.2 min is 25 Jy, the modulation index is unity. The average relative amplitude of the interpulse (IP) is (2.00 pm 0.28% ) of the main pulse. In individual pulses, the amplitude of the interpulse may exceed the amplitude of the main pulse (MP), but this is a rare event. Radiation is observed in almost the entire period of the pulsar. For the first time, the relative amplitude of radiation between the main pulse and the interpulse (radiation bridge) was measured. When averaging for ~10 h, it varies from 0.8 to 1.31% with an average value of (1.04 pm 0.28% ). A high correlation between MP and IP amplitude variations both when averaging profiles over 3.2 min and when averaging over years was found. This correlation is due to refractive interstellar scintillation. The frequency scale of IP diffraction interstellar scintillation was measured for the first time, and that the spectral shapes for IP and MP were shown to be well correlated and have the same frequency scale. There are strong variations in the frequency scale of scintillation ({{f}_{{{text{dif}}}}}) from session to session (time interval from one day) on scales of 200–800 kHz. The refractive scale of scintillation of 1–2 days was determined. A modulation of radiation with a characteristic scale of ~130 days, which, apparently, is also associated with refractive scintillation, was found.

To determine the relative distances and peculiar velocities of 140 groups and clusters of galaxies at low redshifts (z < 0.12), we used the fundamental plane (FP) of early-type galaxies (from the Sloan Digital Sky Survey (SDSS) data). We constructed the Hubble diagram for the relative distances of galaxy groups/clusters versus their radial velocities in the cosmic microwave background (CMB) reference frame in the flat Λ cold dark matter (ΛLCDM) model (Ω_m = 0.3 and H₀ = 70 km s^–1 Mpc^–1). We have found that the standard logarithmic deviation for groups and clusters of galaxies on the Hubble diagram (minus peculiar velocities) is ±0.0173 (N = 140), which corresponds to a deviation of 70 ± 2.8 km s^–1 Mpc^–1 in the Hubble constant. For a sample of galaxy systems (N = 63), the X-ray luminosity of which is in an interval of (0.151‒4) × 10⁴⁴ erg/s, this quantity turned out to be 70 ± 2.1 km s^–1 Mpc^–1. The root-mean-square deviations of peculiar velocities with quadratic accounting for errors are ({{langle V_{{{text{pec}}}}^{2}rangle }^{{1/2}}}) = 714 ± 7 and 600 ± 7 km/s, respectively. For five large superclusters of galaxies from the SDSS region, the average peculiar velocity relative to the CMB reference frame is +240 ± 250 km/s. We detected no outflow of galaxy systems from the void (Giant Void; α ≈ 13^h, δ ≈ 40°, and z ≈ 0.107) formed by groups and clusters of galaxies.

The present survey represents a continuation of our study of high mass star forming regions in the lines of deuterated molecules, the first results of which were published in [1]. This paper present the results of observations of 50 objects in the line of ortho modification of singly deuterated ammonia NH₂D (1_{{11}}^{s}{-} 1_{{01}}^{a}) at a frequency of 85.9 GHz, carried out using the 20-m radio telescope of the Onsala Space Observatory (Sweden). This line is detected in 29 sources. The analysis of obtained data, as well as the fact that the gas density in the investigated sources, according to independent estimates, is significantly lower than the critical density for this NH₂D transition, indicate non-LTE excitation of NH₂D. Based on non-LTE modeling, estimates of the relative content of the NH₂D molecule and the degree of deuterium enrichment were obtain, and the dependencies of these parameters on temperature and velocity dispersion were analyzed with and without taking into account detection limits assuming the same gas density in all sources. An anti-correlation between the NH₂D relative abundances and the kinetic temperature is revealed in a temperature range of 15–50 K. At the same time, a significant decrease in the ratio of the NH₂D/NH₃ abundances with increasing temperature, predicted by the available chemical models, is not observed under the adopted assumptions. An anti-correlation was also revealed between the relative content of the main isotopologue of ammonia NH(_{3}) and the velocity dispersion, while no statistically significant correlation with the kinetic temperature of sources in the same temperature range was found.

In this paper, we analyze and interpret light curves obtained by observing with the HST telescope the transit of exoplanet HD 189733b across the disk of the star. Observations are carried out in a wide wavelength range of 5500–10 500 Å, which makes it possible to identify the relation between the wavelength and the data obtained during the interpretation of the radius of the planet. It is also shown that this dependence can be explained by the presence of a Rayleigh atmosphere on the planet while the possible parameters of this atmosphere are also approximately estimated.

The search for long-term variability of compact components of radio sources B0821+394 and B1812+412 over an interval of ten years was carried out. The LPA LPI radio telescope with an operating frequency of 111 MHz was used for observations. According to our estimates, the characteristic time of variability for both sources is 1.5–2.5 years. It is shown that the observed variability is not related to intrinsic variations in the radiation flux, but is due to refractive scintillation on inhomogeneities of the interstellar medium. From the obtained upper estimates of the apparent angular dimensions of the sources, it follows that the main contribution to the scattering of radio emission is made by turbulent plasma concentrated in sufficiently thin screens, the distance to which does not exceed 300–400 pc.

Ultra-hot Jupiter Kelt9b impels to reconsider existing models of the upper atmospheres of hot exoplanets, which were previously developed using examples of G or M star systems such as HD209458b and GJ436b. The unique conditions of interaction between the radiation of an A-class star and the atmosphere necessitate kinetic modeling of excited levels of elements, primarily the hydrogen atom. Kelt9b shows the absorption for several Balmer lines and lines of a number of heavy elements, the quantitative interpretation of which is an urgent problem. In this study, for the first time, 3D modeling of the atmosphere of a planet with a close location of the Roche lobe is implemented with allowance for the aeronomy and kinetics of excited hydrogen.

A method for studying the secular evolution and stabilization of the shape of rings in small celestial bodies that do not have shepherd satellites is developed. A model of a compound ring consisting of two close, generally non-coplanar elliptical Gaussian rings is constructed. The self-gravitation of the ring is taken into account through the mutual gravitational energy of the boundary rings W_mut. The function W_mut is presented as a series with an accuracy of up to the 4th power of small eccentricities and mutual inclination of the rings. The secular evolution of a compound ring is described by differential equations in special (collective) variables. For rings without a central body (problem 1), a closed system of eight differential equations is obtained using the mutual energy function. The evolution of rings in the azimuthally averaged potential of a rotating triaxial body is also studied (problem 2), for which a second system of eight differential equations is derived. In both problems, besides the general case, two particular ones are considered: (i) the case of coplanar elliptical rings, and (ii) the case of circular rings with a tilt. The theory is applied to study the recently discovered ring of dwarf planet Haumea. It is shown that without taking into account self-gravity, the nodal precession time of the Haumea ring is equal to T_Ω = 12.9 ± 0.7d but taking into account the self-gravity of the ring can reduce this period. It is established that self-gravity does indeed contribute to the preservation of the ring shape without invoking the hypothesis of shepherd satellites. Criteria for the preservation of the ring shape are obtained, which made it possible to estimate the interval for the ratio of the ring mass to the mass of Haumea 10^–4 < m/M < 10^–3. Taking into account the optical thickness of the ring τ ≈ 0.5, it is shown that the Haumea ring with a mass m/M ≈ (1–2) × 10^–4 can consist of ice particles with a size of ({{d}_{0}} approx 0.7{-} 1) m.

Results of a study of physical parameters of stellar population in star formation regions in galaxies with signs of peculiarity NGC 3963 and NGC 7292 are presented. The study was carried out based on the analysis of photometric (UBVRI bands), H(alpha ) and spectroscopic data obtained by the authors, using evolutionary models of stellar population. Among 157 star formation regions identified in galaxies, the young stellar population mass estimates were obtained for 16 of them and the age estimates were obtained for 15. The age of star formation regions clearly correlates with the presence of emission in the H(alpha ) line: H II regions in the galaxies are younger than 6–8 Myr, and the regions without gas emission are older. The studied objects are included in the version 3 of our catalogue of photometric, physical and chemical parameters of star formation regions, which includes 1667 objects in 21 galaxies. Key aspects of the technique used to estimate the physical parameters and different relations between observational and physical parameters of the young stellar population in star formation regions are discussed.