 Subjects -> ASTRONOMY (Total: 94 journals)
|
|
|
- Mass Indices of Meteoric Bodies: II. Evolution of Meteoroid Streams
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: — The calculation results of the evolution of meteoroid streams obtained using the model described by Shustov and Zolotarev (2022) are presented. The model was implemented using the REBOUND software package. The evolution of model meteoroid streams associated with comets 96P/Machholz and 2P/Encke was considered. It was shown that the distribution of mass spectra is formed in the meteoroid stream: the mass index at the center of the stream \(s < 2\) , while at the edge of the stream \(s\) may exceed 2. There are two causes of such changes in the structure of the meteoroid stream: (1) the initial velocity of particle ejection from the comet nucleus strongly depends on the particle size, and small particles move away from the nucleus faster; (2) small particles are more exposed to the action of radiation forces and therefore scatter in space faster than large particles, so the mass index at the center of the stream decreases. These results are consistent with the results obtained by other authors from observations of meteor streams, in particular, the Arietids stream.
PubDate: 2022-03-01
- Globular Cluster as Indicators of Galactic Evolution
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: We have studied the system of globular clusters (GCs) that formed in other galaxies and eventually accreted onto the Milky Way. Thus, the samples of GCs belonging to different tidal streams, obtained on the basis of the latest data from the GAIA observatory, were taken from the literature. We measured the anisotropy of the distribution of these GCs using the tensor of inertia and found that the distribution of GCs in the streams is isotropic. Nevertheless, it can be seen that some of the accreted GCs included into existing samples actually belong to the disk of the Galaxy. To clarify the origin of GCs, we investigated “the age–metallicity” relation. This dependence appeared to be bimodal and its two different branches clearly show the difference between the clusters formed in the streams and in the disk of the Galaxy. Furthermore, we have studied the influence of the large-scale environment of the Galaxy (i.e., the Local Supercluster) on the distribution of satellite galaxies and Galactic GCs. The satellite galaxies of the Milky Way are known to form an anisotropic planar structure, so we included them in our analysis too. An inspection has shown that the plane of the satellite galaxies is perpendicular both to the disk of the Galaxy and the supergalactic plane. For GCs more distant than 100 Kpc, a similar picture is observed.
PubDate: 2022-03-01
- Photometric Behavior of the Herbig Ae Star VX Cas in the Near-Infrared and
Optical Ranges of the Spectrum-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: This paper presents the results of the study of long-term photometric activity in the near infrared spectral region of the young Herbig Ae star VX Cas belonging to the family of irregular UX Ori variables. The infrared data were obtained in 2003–2017 at the Campo Imperatore Observatory (Italy) using the Pulkovo telescope AZT-24 in Johnson’s photometric bands \(JHK\) . Additional optical photometry from various sources was used as well. It was shown that the observed photometric activity of the star in the \(J\) band and partly in the \(H\) band was caused mainly by variations in circumstellar extinction in the protoplanetary disk. In a number of episodes, anticorrelation was observed between brightness variations in the optical \(V\) band and \(H\) and \(K\) bands: the brightness in the \(H\) and \(K\) bands increased with weakening of the brightness in the \(V\) band. This indicates that the gas and dust clouds that screened the star from the observer consisted of hot dust and were located near the sublimation zone.
PubDate: 2022-03-01
- Effect of Dust Evaporation on the Fossil Magnetic Field of Young Stars and
Their Accretion Disks-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: The theory of the fossil magnetic field of young stars and their accretion disks has been verified by comparing the observational data with the results of numerical simulations of the collapse of protostellar clouds. A new model of dust evaporation has been proposed, in which the parameter is not the thickness of the mantles, but the initial ratio of the core radius to the mantle radius of a dust grain. A semi-analytical description of the evolution of the radius distribution of dust grains was constructed. On its basis, the variations in the relative number density of dust grains, as well as the average values of the radius, cross-sectional area, and mass of dust grains, were calculated. It was shown that at the stage of disappearance of dust cores, these averages reach their maxima, but this does not affect the interaction of dust with gas particles, since the dust becomes scarce. Using cloud models W3 (main), NGC 2024, and DR 21 OH1, it has been demonstrated that neglecting dust evaporation underestimates the fossil magnetic field by several times. The possibility of formation of a magnetic compaction at the outer boundary of the zone of strong magnetic field diffusion (dead zone) has been confirmed. It is concluded that a correct calculation of dust evolution, ionization of the medium, and collapse anisotropy makes it possible to match the theoretical and observed magnetic fields of young stars and their accretion disks.
PubDate: 2022-03-01
- Numerical Model to Study Proton Polar Aurorae on Mars
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: — We present a hybrid model and a magnetohydrodynamic (MHD) one for the solar wind plasma flow around Mars, which serve to calculate the flux of protons of the solar wind and the boundary of the induced magnetosphere. These parameters are used as input data for the kinetic Monte-Carlo model of the impact of a proton flux of the undisturbed solar wind on the daytime atmosphere of Mars. This model is intended to be used to determine the energy fluxes and the energy spectra of hydrogen atoms penetrating into the daytime upper atmosphere through the induced magnetosphere boundary. The obtained characteristics allow us to estimate the parameters of proton auroral phenomena, which were recently discovered in the upper atmosphere of Mars. Based on these characteristics, proton aurorae, which were observed with the Imaging UV Spectrograph (IUVIS) onboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, can be calculated. The comparison of the results of these calculations with the observed characteristics opens up a unique opportunity to specify more accurately the properties of the atmosphere and the magnetic field of Mars, as well as enlarges a range of techniques used to determine the solar wind parameters.
PubDate: 2022-03-01
- Dynamic Model of a Non-equilibrium Chemical Composition Formation in the
Shell of Single Neutron Stars-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: The process of a non-equilibrium chemical composition formation during cooling due to neutrino energy loss in the shells of hot, formed neutron stars is considered. A model constructed is to explain the presence of a large quantity of nuclear energy accumulated, which can maintain the X-ray luminosity of such compact objects for a long period of time. The study of the numerically obtained final chemical composition dependence on various parameters of the medium has been carried out.
PubDate: 2022-03-01
- Variations in the Radial Dependence of the Interplanetary Scintillation
Level in the Descending Phase of Solar Cycle 24-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: The results of the long-term (2015–2019) series of interplanetary scintillation observations carried out with the LPA LPI radio telescope at the frequency 111 MHz are presented. We analyzed the radial dependences of the relative level (index) of interplanetary scintillations of the radio source 3C 48, the line of sight to which during the year shifts from low to medium and high heliolatitudes. For all annual series, we showed that the radial dependence of the scintillation index turns out to be flatter than expected for the model of a spherically symmetric medium. The difference is explained by the latitudinal effect, considering the influence of the near-equatorial layer with an increased plasma density. Modeling the low-latitude layer shows that the layer thickness at the phase of the decline in solar activity is, on average, two times greater than near the activity minimum.
PubDate: 2022-02-01
- Barions and ΛCDM Model Problems
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: We examine the inner profiles of the rotation curves of galaxies in the velocity range from dwarf galaxies to Milky-way like galaxies, having maximum of rotation, \({{V}_{{{\text{max}}}}}\) , in the range (30–250) km/s, whose diversity is much larger than that predicted by the \(\Lambda \) CDM model. After showing that the scatter in the observed rotation curves is much larger that predicted by dark matter-only cosmologies, we show how taking into account baryons, through a semi-analytical code, allows to create a a variety of rotation curves in agreement with observation. Simultaneously, we show that the quoted discrepancy does not need for different form of dark matter as advocated by other authors. We finally show how our model can reobtain the rotation curve of remarkable outliers like IC 2574, a 8 kpc cored profile having a challenging, and extremely low rising rotation curve, and UGC 5721 a cusp-like rotation curve galaxy. We suggest treating baryonic physics properly before introducing new exotic features, albeit legitimate, in the standard cosmological model.
PubDate: 2022-02-01
- Motion of Stars in Layered Inhomogeneous Elliptical Galaxies
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: The problem of the spatial motion of a passively gravitating body (PGB) in the gravitational field of a layered inhomogeneous elliptical galaxy (LIEG) is considered on the basis of the previously developed model. It is assumed that a LIEG consists of baryonic mass (BM) and dark matter (DM), which have different laws of density distribution. A star or the center of mass of a globular cluster is taken as the PGB, the motion of which considers the BM and DM attraction. To obtain accurate results, the BM and DM attraction potentials are not expanded in a series, but their exact expressions are taken. An analogue of the Jacobi integral is found, the region of the possible motion of the PGB is determined, and the zero-velocity surfaces are constructed. The stationary solutions (libration points) are found to be stable in the sense of Lyapunov. The results are applied to the elliptical galaxies NGC 4472 (M 49), NGC 4697, and NGC 4374 (M 84).
PubDate: 2022-02-01
- Influence of the Change in the Relative Number of Pores in Activity Cycles
on the Reconstruction of the Sunspot Index-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: An analysis of the relative number of groups in cycles 21–24 based on the digitization of observations of sunspots at the Locarno Observatory (Locarno, Switzerland) was performed. In the Zurich classification of sunspot groups, there are classes from A to J. The classes correspond to the process of development and decay of sunspot groups. Class A and B groups correspond to single pores or small pore clusters (class A) and bipolar group (class B). For the reconstruction of solar indices, the relative number of groups (A + B) is of great importance. We found significant variations in the relative number of spot groups (A + B) in the activity cycles. If the relative number of groups (A + B) at the activity minima is 45–50%, then a decrease to 25–30% at the activity cycle maxima is observed. In the original spot index R, proposed by R. Wolf, pores were not considered, and many cores united by one penumbra were counted as one spot. After 1893, at the suggestion of A. Wolfer, the method of calculating the sunspot index changed. The pores and all individual cores in the spots began to be considered – this index is denoted by Rz. It is believed that between the spot indices of the Wolf (R) and Wolfer (Rz), there is a constant transition coefficient close to R/Rz = 0.6. We found that this assumption is incorrect, and R/Rz depends on the amplitude of the activity cycle, varying for the N19 cycle R19~ 0.34, and for the period of the grand minimum RMM ~ 0.64.
PubDate: 2022-02-01
- Mass Indices of Meteoric Bodies: I. Formation Model of Meteoroid Streams
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: It is known from observations that the mass spectra of meteoric bodies (meteoroids) that cause the phenomena of sporadic meteors and bodies in meteor showers are close in differential form to dN ∝ M–s dM, while the mass index s ≈ 2 for sporadic meteors and s < 2 (1.5−1.8) for meteor showers. We have analyzed the causes of this difference. We assume that the value of the index s ≈ 2 implies the randomness of the meteoroid stream formation both as a result of the decay of comets and of collisions of asteroids and larger meteoroids. The deviation of the index from 2 is due to the influence of the further evolution of meteoroid streams. This study considers the formulation of the first part of the problem of the evolution of the mass spectrum of bodies in meteoroid streams. This part refers to the determination of the velocity field of particles of various masses escaping the comet nucleus, i.e., substantiation of the choice of input parameters of the corresponding numerical model for calculating the further evolution of the meteoroid stream. An important feature is the consideration of an ensemble of particles of various sizes in the range of sizes (masses) that allow the use of the most abundant radar data on determining the meteoroid masses for comparison.
PubDate: 2022-02-01
- Study of the Magnetic Properties of Sunspot Umbrae
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: The paper presents the results of the study of sunspots, obtained by the authors and other researchers in recent years. The results regarding the atmosphere above sunspot umbrae, based on the observational data in the spectral lines of the upper chromosphere and lower corona, are discussed. It is shown that individual parameters of the profile of these lines differ in leading and trailing sunspots. A hypothesis about the relationship between the parameters of the profiles of these spectral lines and the parameters of the magnetic field in sunspot umbrae is stated and tested. A comparative analysis of the magnetic properties of the umbrae of leading and trailing sunspots in active regions (ARs) without explosive processes (EPs, id est, formation of coronal mass ejection with solar flare) is carried out. For the analysis, only pairs of magnetically coupled (connected by magnetic field lines) leading and trailing sunspots were selected. It is shown that the values of a number of magnetic field parameters in sunspot umbrae and the character of the relationship between them depend on the type of the sunspots. In particular, in the umbrae of leading and trailing sunspots of close areas, the maximum and average magnitudes of the magnetic induction are different. The dependences of the minimum angle of inclination of the field lines to the radial direction from the center of the Sun and the average inclination angle of the field lines on the umbra areas of leading and trailing sunspots are also different. For magnetically coupled leading and trailing sunspots, it is shown that the distances from the center of the umbra of each type of sunspots to the main polarity separation line of the photospheric field in ARs are different. The paper also discusses the time variation of various magnetic field parameters of the sunspot umbra separately for single and magnetically coupled sunspots, as well as sunspots of magnetically coupled ARs, which we defined as magnetic activity complexes (MACs). The evolution of the magnetic characteristics of sunspots, including sunspots in the MACs, during a radical rearrangement of the magnetic configuration is studied. The influence of EPs on the characteristics of the magnetic field in sunspots is revealed. One of the objectives of this work was to reveal the difference between the properties of sunspots in ARs without EPs and in ARs with various activities, e.g., with solar flares and the formation of coronal mass ejections.
PubDate: 2022-02-01
- Erratum to: Statistical Analysis of the Results of 20 years of Activity of
the International VLBI Service for Geodesy and Astrometry-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: An Erratum to this paper has been published: https://doi.org/10.1134/S1063772922020032
PubDate: 2022-01-01
DOI: 10.1134/S1063772922020032
- Solar Wind from Maximum to Minimum for Cycle 24 in Interplanetary
Scintillation Monitoring Data-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: A comparison is made of the data from the annual series of interplanetary scintillation monitoring performed at the maximum (2015) and minimum (2019) of solar activity. The observations were carried out with the LPA LPI radio telescope at the frequency 111 MHz. We showed that the time-of-day dependences of the scintillation level averaged over monthly intervals for the summer months at the minimum and maximum are approximately the same. For the winter months, at the decay phase and at the minimum of activity, an annual periodicity in the scintillation level is observed; at the maximum of activity, there is no periodicity. The results obtained can be explained by a combination of the cyclic dynamics of the global structure of the solar wind and the change in the location of the solar wind regions probed in the experiment during the year.
PubDate: 2022-01-01
DOI: 10.1134/S1063772922010036
- First Telescope of the Russian–Cuban Observatory
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Beginning of operation of the first Russian–Cuban Observatory telescope, a wide-field 20-cm robotic telescope installed at the observational site optical station in Havana, Republic of Cuba, is reported. The general view of the telescope is shown and attached equipment is described. The “first light” obtained using a 20-cm telescope is demonstrated and briefly discussed. Multi-task observational projects supposed to be conducted using mentioned RCO telescope are described. Russian–Cuban complexication scheme is described and some of its features are briefly discussed.
PubDate: 2022-01-01
DOI: 10.1134/S1063772922020019
- Comparison of Different Estimates of the Accuracy of Forecasts of the
Earth’s Rotation Parameters-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Improvement of the prediction accuracy of the Earth’s rotation parameters (ERP) is one of the main problems of applied astrometry. In order to solve this problem, various approaches are used and in order to select the best one, comparison of the accuracy of the forecasts obtained by different methods at different centers of analysis are often carried out. In such comparisons, various statistical estimates of the forecast errors are used, based on the analysis of the differences between the predicted and final values of ERP. In this paper, we compare several estimates, such as root mean square error, mean error, median error, and maximum error. It is shown that a direct relationship between the estimates of the forecast accuracy obtained by these methods does not always exist. Therefore, in order to obtain the most informative results of comparison of the accuracy of different forecast methods, it is recommended to use the studies that compare the series of ERP forecasts, especially short-term ones, several estimates together.
PubDate: 2022-01-01
DOI: 10.1134/S1063772922020068
- Dynamical Properties of Body with Variable Mass in a Fifth-degree
Hénon–Heiles System-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: The aim of this work is to investigate the motion properties of the infinitesimal body in the frame of the fifth-degree generalized Hénon–Heiles (GHH) potential. We determine the equations of motion of the infinitesimal body, where its mass varies according to the Jeans law, within the framework of the GHH potential. We illustrate numerically the positions of stationary points and their stability, and we found that all these points are unstable. Further, the dynamical features such as Poincaré surfaces of section, the trajectory allocations, the basins of attraction, the permitted and prohibited regions of motion are studied for each stationary point.
PubDate: 2022-01-01
DOI: 10.1134/S1063772922010012
- Discovery of Emission Pulses from Magnetar SGR 1935+2154
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: In the paper, observation results of the magnetar SGR 1935+2154 at the frequency 111 MHz by the LPA (BSA) FIAN radio telescope are presented. For the search of single non-periodic pulses, we used data recorded in the six-frequency channel mode with a temporal resolution of 0.1 s in the receiver band 110.25 ± 1.25 MHz. As a result of data analysis for the period from September 1, 2019 to March 1, 2021, a pulse was detected with a dispersion measure \(DM = 320 \pm 10\) pc/cm3, scattering value \(\tau \sim 340\) ms, and a fluence \(f\sim 300\) Jy ms. To search for periodic pulses, we used data recorded in the 32-channel mode in the receiver band 109–111.5 MHz in January–February and October–December, 2020. As a result, in two sessions, periodic radiation was found with a period of 3.247 s, an amplitude of 40 mJy, and dispersion measure DM = 320 pc/cm3.
PubDate: 2022-01-01
DOI: 10.1134/S1063772922010061
- Nonequilibrium Neutronization and Large-Scale Convection in Gravitational
Collapse-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Most of the energy released by the gravitational collapse of the cores of massive stars is carried away by neutrinos. The self-consistent problem of gravitational collapse is solved using 2D gas dynamics considering the spectral transport of neutrinos in the flux-limited diffusion. It is shown that large-scale convection develops in the region near the neutrinosphere and leads to an increase in the average neutrino energy up to 15–18 MeV, which is 1.5 times higher than the results of 1D calculations. This study improves a simple model of neutronization in the central opaque region, which is applicable, strictly speaking, only in the transparent region. The 2D model correctly reproduces the high chemical potential of degenerate electrons ~60 MeV at the center with a high density of matter, as in spherically symmetric calculations with exact account of the weak interaction. Since neutronization at the center is reversible due to trapped neutrinos, the instability development in the center is suppressed, and the high chemical potential of electrons at the center in the refined neutronization model does not affect the energy of outgoing neutrinos. The obtained neutrino energies are important both for explaining the supernova phenomenon and for setting up an experiment to detect neutrinos from a supernova.
PubDate: 2022-01-01
DOI: 10.1134/S1063772922010024
- In-phase Variations in the Parameters of the Earth’s Pole Motion and the
Lunar Orbit Precession-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: We found an oscillatory process of the Earth’s pole associated with the precession motion of the Moon’s orbit using numerical processing a series C01 of observational data and measurements of the Earth’s pole motion over a long time interval starting from 1900. Several methods have been proposed for converting the coordinates of the Earth’s pole to a system in which its motion occurs in phase with a change in the orientation of the plane of the lunar orbit in relation to the Earth’s equator. The performed transformation depends only on the average parameters of the Earth’s pole motion and does not explicitly depend on time. In this system, we showed that the polar radius oscillates in phase with oscillations of the inclination angle of the lunar orbit plane to the Earth’s equator, and the polar angle oscillations occur in phase with the deviation along the equator of the intersection point of the lunar orbit with the equator.
PubDate: 2022-01-01
DOI: 10.1134/S1063772922020081
|
Hybrid journal (It can contain Open Access articles)
