Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 51)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 39)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 63)
Artificial Satellites     Open Access   (Followers: 23)
Astrobiology     Hybrid Journal   (Followers: 14)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 6)
Astronomical Journal     Full-text available via subscription   (Followers: 8)
Astronomical Review     Open Access   (Followers: 4)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 48)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 60)
Astronomy and Astrophysics     Open Access   (Followers: 32)
Astronomy and Computing     Hybrid Journal   (Followers: 2)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 15)
Astronomy Studies Development     Open Access   (Followers: 12)
Astroparticle Physics     Hybrid Journal   (Followers: 8)
Astrophysical Bulletin     Hybrid Journal   (Followers: 3)
Astrophysical Journal     Full-text available via subscription   (Followers: 19)
Astrophysical Journal Letters     Full-text available via subscription   (Followers: 14)
Astrophysical Journal Supplement Series     Full-text available via subscription   (Followers: 14)
Astrophysics     Hybrid Journal   (Followers: 29)
Astrophysics and Space Science     Hybrid Journal   (Followers: 46)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 56)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 12)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 11)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 24)
Colloid Journal     Hybrid Journal   (Followers: 3)
Comptes Rendus Physique     Full-text available via subscription   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 3)
COSPAR Colloquia Series     Full-text available via subscription   (Followers: 11)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 55)
Earth, Planets and Space     Open Access   (Followers: 74)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 39)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 7)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 6)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 41)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 12)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 4)
Gravitation and Cosmology     Hybrid Journal   (Followers: 4)
Icarus     Hybrid Journal   (Followers: 75)
International Journal of Advanced Astronomy     Open Access   (Followers: 28)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 19)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 29)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 13)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 12)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 7)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 19)
Journal of Astrobiology & Outreach     Open Access   (Followers: 3)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astronomical Telescopes, Instruments, and Systems     Hybrid Journal   (Followers: 5)
Journal of Astrophysics     Open Access   (Followers: 26)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 52)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 199)
Journal of Cosmology and Astroparticle Physics     Hybrid Journal   (Followers: 38)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 179)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 177)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 22)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 10)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 4)
MNASSA : Monthly Notes of the Astronomical Society of South Africa     Full-text available via subscription   (Followers: 1)
Molecular Astrophysics     Full-text available via subscription   (Followers: 1)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 14)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal  
Nature Astronomy     Hybrid Journal   (Followers: 8)
New Astronomy     Hybrid Journal   (Followers: 27)
New Astronomy Reviews     Full-text available via subscription   (Followers: 17)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 5)
Open Astronomy     Open Access   (Followers: 2)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 101)
Planetary Science     Open Access   (Followers: 52)
Proceedings of the International Astronomical Union     Full-text available via subscription   (Followers: 2)
Publications of the Astronomical Society of Australia     Hybrid Journal   (Followers: 2)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 3)
Publications of the Astronomical Society of the Pacific     Full-text available via subscription   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 17)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 29)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 2)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 34)
Solar System Research     Hybrid Journal   (Followers: 14)
Space Science International     Open Access   (Followers: 193)
Space Science Reviews     Hybrid Journal   (Followers: 97)
Space Weather     Full-text available via subscription   (Followers: 24)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 5)
Similar Journals
Journal Cover
Astronomy Letters
Journal Prestige (SJR): 0.452
Citation Impact (citeScore): 1
Number of Followers: 22  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1562-6873 - ISSN (Online) 1063-7737
Published by Springer-Verlag Homepage  [2626 journals]
  • Production of Heavy Elements during the Explosion of a Low-Mass Neutron
           Star in a Close Binary
    • Abstract: The nucleosynthesis of heavy elements in the scenario for the evolution of a close binary of neutron stars differing greatly in mass is considered. In contrast to the scenario for the merger of two neutron stars of comparable masses considered repeatedly in the literature, the evolution of such a binary at the final stage consists in a rapid mass transfer to the more massive star and an explosive disruption of the low-mass component. We provide the details of the explosion and calculate the abundances of the heavy elements produced in this process for various initial conditions.
      PubDate: 2020-08-01
  • Active Galactic Nuclei among Polar-Ring Galaxies
    • Abstract: Based on SDSS data, we consider the fraction of active galactic nuclei among polar-ring galaxies. We have found evidence for an excess of Seyfert galaxies and LINERS among polar-ring galaxies compared to ordinary objects. The observed nuclear activity of polar-ring galaxies may be associated with the accretion of gas from the region of the polar structures onto the central galaxies.
      PubDate: 2020-08-01
  • Using Spherical Harmonics in the Galactocentric Coordinate System to Study
           the Kinematics of Globular Star Clusters
    • Abstract: The technique of spherical harmonics, both scalar and vector ones, has long been applied to analyze the astronomical data on a sphere, for example, in the representation of systematic errors, in stellar kinematics. Up to now, spherical harmonics have been used exclusively in heliocentric coordinate systems: the equatorial or Galactic one. To study the kinematics of the entire Galaxy (and not only the solar neighborhood), it is reasonable to pass to the Galactocentric coordinate system. The second release of the Gaia catalogue does not yet allow such an analysis to be performed for individual stars due to the relatively low accuracy of the parallaxes. However, such a study seems possible for globular star clusters, despite their small number. Although the kinematics of globular clusters was studied in detail in many papers, we want to test the method of analyzing the Galactocentric proper motions and radial velocities using spherical harmonics based on data from this catalogue.
      PubDate: 2020-08-01
  • High-Resolution Optical Spectroscopy of the Post-AGB Supergiant V340 Ser (
           $${\mathbf{=}}$$ IRAS 17279 $$\mathbf{-}$$ 1119)
    • Abstract: Evidence of wind variability and velocity stratification in the extended atmosphere has been found in the spectra of the supergiant V340 Ser ( \({=}\) IRAS 17279 \(-\) 1119) taken at the 6-m BTA telescope with a resolution \(R\geq 60\,000\) . The H \(\alpha\) line has a P Cyg profile whose absorption component ( \(V_{\odot}={+}34\) km s \({}^{-1}\) ) is formed in the upper layers of the expanding atmosphere close the circumstellar medium. For four dates the mean velocity has been derived from the positions of 300–550 symmetric metal absorptions with an accuracy better than \({\pm}0.1\) km s \({}^{-1}\) : \(V_{\odot}=59.30\) , \(60.09\) , \(58.46\) , and \(55.78\) km s \({}^{-1}\) . A lot of low-excitation metal lines have an inverse P Cyg profile. The mean positions of their emission components, \(V_{\odot}=46.3\pm 0.4\) km s \({}^{-1}\) , differ systematically from the velocity inferred from symmetric absorptions, suggesting the presence of a velocity gradient in the supergiant’s extended atmosphere. The multicomponent profile of the Na I D lines contains the interstellar, \(V_{\odot}={-}11.2\) km s \({}^{-1}\) , and circumstellar, \(V_{\odot}={+}10\) km s \({}^{-1}\) , components and the component forming in the upper atmospheric layers, \(V_{\odot}={+}34.0\) km s \({}^{-1}\) . The mean velocity from 20–30 diffuse interstellar bands (DIBs) identified in the spectra, \(V_{\odot}\textrm{(DIBs)}={-}11.6\pm 0.2\) km s \({}^{-1}\) , agrees with the velocity from interstellar Na I and K I components. The equivalent width of the oxygen triplet \(\textrm{W(O\,I 7774)}=1.25\) Å corresponds to an absolute magnitude of the star \(Mv\approx{-}4.6^{m}\) , which, given the total (interstellar \(+\) circumstellar) extinction, leads to a distance to the star \(d\approx 2.3\) kpc.
      PubDate: 2020-08-01
  • Evolutionary Status and Fundamental Parameters of the Cepheid V1033 Cyg
    • Abstract: On the basis of consistent stellar evolution and nonlinear stellar pulsation calculations, the Cepheid V1033 Cyg is shown to be the post-main sequence star at the first crossing of the instability strip during the gravitational contraction of the helium core. The observed light variability of V1033 Cyg is due to the radial oscillations in the fundamental mode. The best agreement (within one percent) between recent observations and the theoretical estimate of the period change rate was obtained for the evolutionary sequence with stellar mass \(M=6.3M_{\odot}\) and helium and heavier element fractional abundances \(Y=0.28\) and \(Z=0.022\) , respectively. The age of the star, the luminosity, the radius, the effective temperature and the surface gravity are \(t_{\textrm{ev}}=5.84\times 10^{7}\) yr, \(L=2009L_{\odot}\) , \(R=45.6R_{\odot}\) , \(T_{\textrm{eff}}=5726\) K, \(\log g=1.92\) .
      PubDate: 2020-08-01
  • Non-LTE Effects in Rubidium Lines in Cool Stars
    • Abstract: The formation of the rubidium resonance lines is considered by taking into account the effects of departures from local thermodynamic equilibrium (LTE). A rubidium model atom has been constructed using 29 Rb I levels and the Rb II ground level. Non-LTE calculations have been performed for a grid of model atmospheres with \(T_{\textrm{eff}}\) from 3500 to 6500 K, \(\log g\) from 1.0 to 5.0, [Fe/H] from \({-}1.0\) to \({+}0.5\) , \(V_{t}=1.0\) km s \({}^{-1}\) , and a relative rubidium abundance \(\textrm{[Rb/Fe]}=0.0\) . It is shown that disregarding the non-LTE effects can lead to significant errors in the abundance of this element. The non-LTE corrections for dwarf stars with effective temperatures below 4000 K depend critically on the inclusion of collisional interactions with hydrogen atoms. The differences in rubidium abundance when using quantum-mechanical calculations and Drawin’s theoretical approximation to take into account the collision rates of atoms with hydrogen atoms can reach 0.17 dex. The rubidium abundance has been determined from its lines in the solar spectrum, \(\textrm{(Rb/H)}=2.35\pm 0.05\) , which virtually coincides with the rubidium abundance deduced from the analysis of meteorites, \(\textrm{(Rb/H)}=2.36\pm 0.03\) .
      PubDate: 2020-08-01
  • The First Orbits of Six Wide Double Stars in the Solar Neighborhood Based
           on Gaia DR2 Observations
    • Abstract: The apparent motion parameter (AMP) method is designed to determine the orbits of wide pairs of double stars with orbital periods of hundreds and thousands of years. This is a dynamical method using all that is known about the star at one moment to reconstruct its complete orbit within the two-body problem. The Gaia DR2 catalog contains all of the data for epoch 2015.5 that are needed to use the AMP method if the relative motion reflects an unperturbed orbital motion. We demonstrate the possibilities of the method to determine the orbits of individual stars. Six stars have been investigated. For the triple star ADS 7034 we have determined the orbit of the inner pair, the set of orbits of the outer pair, and the stability region of the triple system for the first time. Using the double star ADS 9357 as an example, we show that for the determination of the orbits of individual stars the AMP method has an advantage over the geometrical methods using the Thiele–Innes equations on short arcs covered by observations. The orbits with periods more than 1000 years have been determined for the first time for three stars: ADS 7588, ADS 8561, and ADS 9048. For WDS 14051+4913 it is impossible to determine a reliable orbit, a preliminary family of orbits has been obtained, and a companion is suspected. We give a list of problem stars for which the orbits have not been determined, but the presence of a companion is possible.
      PubDate: 2020-08-01
  • Internal Structure of the Jets from Young Stars Simulated at Plasma Focus
    • Abstract: The laboratory simulations of jets from young stars that have been carried out for many years at plasma focus facilities allow the internal structure of the active regions emerging during the interaction of the jet with the surrounding plasma to be studied in detail. We have found a new wide class of solutions for the equations of ideal magnetohydrodynamics describing the closed axisymmetric stationary flows that are apparently realized in the active regions. Such flows are shown to well reproduce the internal structure of the plasma outflows observed in laboratory simulations of astrophysical jets.
      PubDate: 2020-07-01
  • Optical Spectroscopy of SRG/eROSITA Objects with 2.5-m Telescope at the
           Caucasus Mountain Observatory of the SAI MSU
    • Abstract: Based on observations with the new transient double-beam spectrograph (TDS) at the 2.5-m telescope of the Caucasus Mountain Observatory of SAI MSU, we have determined the types and found the redshifts for six new X-ray sources (four quasars and two galaxy clusters) detected by the SRG space observatory during the Lockman Hole observations at the eROSITA performance verification phase. We show that the TDS allows the spectra of objects \({\sim}20^{m}\) to be taken in 2 h of observations with a signal-to-noise ratio higher than 5 and a resolution \(R\sim 1500\) . The types and redshifts of the objects determined from our spectroscopic observations agree well with the predictions based on photometric data using the SRGz automatic classification system.
      PubDate: 2020-07-01
  • Collisional Pumping of OH Masers near Supernova Remnants
    • Abstract: The collisional pumping of OH masers in non-dissociative C-type shocks near supernova remnants is considered. The emergence of maser emission in OH lines is investigated for various shock parameters—the shock speed, the preshock gas density, the cosmic-ray ionization rate, and the magnetic field strength. The largest optical depth in the 1720 MHz line is reached at high gas ionization rates \(\zeta\geq 10^{-15}\) s \({}^{-1}\) , an initial density \(n_{\textrm{H,0}}\leq 2\times 10^{4}\) cm \({}^{-3}\) , and a shock speed \(u_{\textrm{s}}\geq 20\) km s \({}^{-1}\) . According to our calculations, there is also a level population inversion for the 6049 and 4765 MHz transitions of excited OH rotational states. However, the optical depth in these lines is small for all of the investigated shock parameters, which explains the non-detection of maser emission in these lines in supernova remnants.
      PubDate: 2020-07-01
  • Study of the Galactic Rotation Based on Masers and Radio Stars with VLBI
           Measurements of Their Parallaxes
    • Abstract: Based on published data, we have produced a sample of 256 radio sources whose trigonometric parallaxes and proper motions were measured by VLBI. This sample contains Galactic masers associated with massive protostars and stars in active star-forming regions. It also includes young low-mass stars from the Gould Belt region whose radio observations were performed in continuum. Based on this, most complete sample of sources to date, we have estimated the velocities \(U_{\odot}\) , \(V_{\odot}\) , \(W_{\odot}\) and the parameters of the angular velocity of Galactic rotation \(\Omega_{0},\Omega^{(1)}_{0},\ldots,\Omega^{(4)}_{0}\) and obtained a new estimate of the distance from the Sun to the Galactic center, \(R_{0}=8.15_{-0.20}^{+0.04}\) kpc. The parameters of the Galactic spiral density wave have been found from the series of radial, \(V_{R}\) , and residual tangential, \(\Delta V_{\textrm{circ}}\) , velocities of stars. The amplitudes of the radial and tangential velocity perturbations are \(f_{R}=7.0\pm 0.9\) km s \({}^{-1}\) and \(f_{\theta}=3.8\pm 1.1\) km s \({}^{-1}\) , the perturbation wavelengths are \(\lambda_{R}=2.3\pm 0.2\) kpc and \(\lambda_{\theta}=2.0\pm 0.4\) kpc, and the Sun’s phases in the spiral density wave are \((\chi_{\odot})_{R}=-163^{\circ}\pm 9^{\circ}\) and \((\chi_{\odot})_{\theta}=-137^{\circ}\pm 10^{\circ}\) for the adopted four-armed spiral pattern.
      PubDate: 2020-07-01
  • Spectroscopy of B and Be Stars in the Young Open Star Cluster NGC 581 (M
    • Abstract: Based on moderate-resolution spectra in the range 4200–5200 Å, we have studied B and Be stars in the young open star cluster NGC 581. The temperatures of the program stars have been derived by the differential method with the choice of simple spectroscopic parameters for a number of lines and their comparison with the analogous parameters of a large sample of B stars for which accurate estimates of \(T_{\textrm{eff}}\) were obtained through a non-LTE analysis of their atmospheres. Applying this method to our sample of objects has allowed the cluster age, \(t=22\pm 1\) Myr, and the cluster distance modulus, \((m-M)_{0}=12.4^{m}\) , to be determined with confidence. We have studied the spectroscopic variability of the emission spectra for four Be stars in the cluster. All of them are shown to have a long-term variability of the profiles typical of classical Be stars.
      PubDate: 2020-07-01
  • Results of the First Year of the 3BS Polar Search Program
    • Abstract: We present the results of the first year of searching for polar candidates within the 3BS (3-Band Survey) program using medium-band filters. Observational data for 84 selected objects from the catalog of cataclysmic variables of the CRTS DR1 sky survey were obtained while implementing the program. A dwarf nova during its outburst and a polar were detected. The available archival data are analyzed. The dwarf nova is of the U Gem or Z Cam type and contains a massive secondary component with \(M_{2}=0.94\pm 0.04M_{\odot}\) . For the polar found we have estimated the orbital period \(P_{O}=0\overset{d}{.}054437\) and calculated the magnetic field strength of the white dwarf \(B\approx 32\) MG.
      PubDate: 2020-07-01
  • Graph Dynamics of Solar Active Regions: Morse–Smale Complexes and
           Multiscale Graphs of Magnetograms
    • Abstract: We discuss the model for the evolution of an active region (AR) in which the graph constructed from the singular points of the magnetic field codes the AR magnetic patterns. The AR dynamic scenarios are mapped by the discrete structure of the network formed from the maxima, minima, and saddle points of the magnetic field. The AR dynamics leads to a rearrangement of the graph, graph dynamics. We discuss two graphs. The first of them is the graph of a Morse–Smale complex. It is a cellular gradient model of the magnetic field each cell of which contains a maximum, a minimum, and two saddle points. The Morse–Smale complex admits a simplification (editing) with prescribed detail that preserves the field topology. The second graph codes the AR dynamics simultaneously on different scales, in the so-called scale-space. This space is formed by a sequence of convolutions of the original magnetogram with a Gaussian kernel, so that the blurring scale is its additional coordinate. Non-Morse singular points, with a degenerate Hessian and Laplacian, are considered in each scale-space layer. The curves connecting these points in different scales form the critical paths whose vertices are called top points. The graph constructed from these points codes the structure of the degenerate AR field structures on different scales. We propose an efficient method of calculating the critical paths using a Jacobi set. The pre-flare regimes are believed to be associated with a significant change in the field topology, which controls the graph dynamics. Consequently, they must be accompanied by noticeable variations in the spectrum of eigenvalues for the discrete Laplacian of the graph (Kirchhoff–Laplace matrix). As an example, we present the evolution of the spectra for these graphs constructed from the magnetograms of the flaring AR 12673. The SDO/HMI magnetograms of the AR for the scalar line-of-sight (LOS) component served as the data. The possible connection of large variations in the spectrum with succeeding X flares is discussed.
      PubDate: 2020-07-01
  • Galactic Rotation Parameters Based on Stars from Active Star-Forming
           Regions with Data from the Gaia DR2 Catalogue
    • Abstract: We have studied a sample of more than 25 000 young stars with proper motions and trigonometric parallaxes from the Gaia DR2 catalogue. The relative errors of their parallaxes do not exceed 10 \(\%\) . The selection of stars belonging to active star-forming regions was made by Marton et al. based on data from the Gaia DR2 catalogue by invoking infrared measurements from the WISE and Planck catalogues. Low-mass T Tauri stars constitute the majority of sample stars. The following parameters of the angular velocity of Galactic rotation have been found from them: \(\Omega_{0}=28.40\pm 0.11\) km s \({}^{-1}\) kpc \({}^{-1}\) , \(\Omega^{\prime}_{0}=-3.933\pm 0.033\) km s \({}^{-1}\) kpc \({}^{-2}\) , and \(\Omega^{\prime\prime}_{0}=0.804\pm 0.040\) km s \({}^{-1}\) kpc \({}^{-3}\) . The Oort constants are \(A=15.73\pm 0.32\) km s \({}^{-1}\) kpc \({}^{-1}\) and \(B=-12.67\pm 0.34\) km s \({}^{-1}\) kpc \({}^{-1}\) , while the circular rotation velocity of the solar neighborhood around the Galactic center is \(V_{0}=227\pm 4\) km s \({}^{-1}\) for the adopted Galactocentric distance of the Sun \(R_{0}=8.0\pm 0.15\) kpc.
      PubDate: 2020-06-01
  • Ice Permafrost ‘‘Oases’’ Close to Martian Equator: Planet Neutron
           Mapping Based on Data of FREND Instrument Onboard TGO Orbiter of
           Russian-European ExoMars Mission
    • Abstract: We present the first results of Mars neutron sounding by FREND instrument onboard ESA’s Trace Gas Orbiter data analysis. Neutron flux mapping is performed with high spatial resolution, which allows to match epithermal neutron flux variation with relief’s geomorphological structures. Local regions with suppressed neutron flux indicate the presence of considerable amount of hydrogen atoms in the surface material, which is supposedly part of water molecules. Local regions in the equatorial latitudes of the planet with significant decrease of neutron flux are discovered, which points to large mass fraction of water ice in the soil material, ranging from tens to 100 \(\%\) . Considering high water content, these regions are named ice permafrost ‘‘oases.’’ Estimates of ice mass fraction for 7 such regions are obtained based on neutron measurements analysis and end-to-end numerical modeling of the entire physical process of neutron sounding by FREND on Mars orbit. Possible reasons for formation of such ‘‘oases’’ and their significance for future Mars exploration are discussed.
      PubDate: 2020-06-01
  • Modeling the Atmospheres of Tidally Locked Super-Earths Orbiting Low-Mass
           Host Stars Using a Nonhydrostatic General Circulation Model
    • Abstract: We present the results of our numerical simulations of the general circulation in the atmosphere of a hypothetical super-Earth within a model based on the solution of the complete system of hydrodynamic equations. The MIPT/PGI GCM model used for our computations has already been successfully adopted to describe the general circulation of the atmosphere of Venus. The model features high resolution and the absence of linear viscosity. The atmospheric gas is a mixture of gases in some constant proportion and the influence of the aerosol component on the equation of state may be neglected. The Newtonian relaxation scheme is used to describe the processes related to heat transfer. We have found that the westerly zonal superrotation, which can manifest itself in the form of equatorial and two mid-latitude jets, is the main mechanism of circulation in the atmosphere. The positions and intensities of the mid-latitude jets are largely determined by the molecular weight of the atmosphere and the equator–pole temperature contrast. We show the trends reflecting these changes. In the case of a tidally locked super-Earth we also detect a stable equatorial jet perturbed by a Kelvin wave. The intensity of the perturbations has been found to increase with decreasing molecular weight of the atmosphere. We perform our simulations in the framework of a simple greenhouse model.
      PubDate: 2020-06-01
  • Ion Acceleration at the Front of Nonlinear Whistlers
    • Abstract: We have solved the problem of the acceleration of ions (protons) incident on the front of a nonlinear whistler for which the structure of its electromagnetic fields is assumed to be known and defined by the relations derived by us previously. We have established the dependence of the energy to which the protons are accelerated on the angle between the whistler propagation direction and the direction of the external magnetic field and on the whistler speed. The results obtained are applied to the Earth’s bow shock by assuming that the bow shock front has the structure of a nonlinear whistler. We show that the protons are accelerated at the Earth’s bow shock front to 45 keV and end up with such energies upstream of the bow shock in the foreshock region. In our opinion, being scattered by the oscillations existing in the foreshock, these energetic protons form a population of so-called diffuse ions upstream of the bow shock.
      PubDate: 2020-06-01
  • The Lyman-Alpha Forest as an Indicator of Large-Scale Structure Elements
    • Abstract: We propose a method of analyzing the absorption spectra of quasars that allows the physical parameters of absorbing clouds, absorbers, to be roughly estimated: their masses, sizes, and mean densities. An analysis of three representative catalogs of the Lyman-alpha ( \(Ly_{\alpha}\) ) forest and metal absorption line systems confirms that these observations refer to two types of objects with different properties, each of which forms a one-parameter sequence. The parameters of the metal absorption line systems are consistent with the corresponding estimates of the parameters of galaxies. The parameters of the \(Ly_{\alpha}\) forest differ significantly from the galactic ones, but are close to the parameters of a large number of halos presented in numerical models. Possible reasons for the emergence of two one-parameter systems of halos with different properties are discussed.
      PubDate: 2020-06-01
  • Deuterated Isotopologues of Water and Methanol in Star-Forming Regions
    • Abstract: We consider the evolution of the abundance of singly and doubly deuterated isotopologues of water and methanol in a typical protostellar cloud. The main processes determining their abundance in various regions of the cloud have been revealed. We show that the abundances of the deuterated isotopologues can exceed the abundance of the main molecules in a number of cases.
      PubDate: 2020-06-01
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762

Your IP address:
Home (Search)
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-