Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 49)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 50)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 67)
Artificial Satellites     Open Access   (Followers: 21)
Astrobiology     Hybrid Journal   (Followers: 11)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 7)
Astronomical Review     Open Access   (Followers: 5)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 49)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 67)
Astronomy and Computing     Hybrid Journal   (Followers: 6)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 22)
Astronomy Studies Development     Open Access   (Followers: 15)
Astroparticle Physics     Hybrid Journal   (Followers: 10)
Astrophysical Bulletin     Hybrid Journal   (Followers: 4)
Astrophysics     Hybrid Journal   (Followers: 35)
Astrophysics and Space Science     Hybrid Journal   (Followers: 49)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 60)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 13)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 15)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 25)
Colloid Journal     Hybrid Journal   (Followers: 2)
Comptes Rendus : Physique     Open Access   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 6)
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 142)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 47)
Earth, Planets and Space     Open Access   (Followers: 77)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 38)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 8)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 4)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 40)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 3)
Gravitation and Cosmology     Hybrid Journal   (Followers: 6)
Icarus     Hybrid Journal   (Followers: 71)
International Journal of Advanced Astronomy     Open Access   (Followers: 21)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 22)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 36)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 8)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 14)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 20)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astrophysics     Open Access   (Followers: 33)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 58)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 133)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 115)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 134)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 25)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 11)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 5)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal   (Followers: 2)
Nature Astronomy     Hybrid Journal   (Followers: 14)
New Astronomy     Hybrid Journal   (Followers: 26)
New Astronomy Reviews     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 4)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 106)
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: 3)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 38)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 3)
Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 4)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 29)
Solar System Research     Hybrid Journal   (Followers: 15)
Space Science International     Open Access   (Followers: 117)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Space Weather     Full-text available via subscription   (Followers: 27)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 6)
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  [2469 journals]
  • GX 339-4: Is the Hot-Flow Precession Model Consistent with the Infrared
           Variability in Low-Mass X-ray Binaries'

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      Abstract: During accretion-induced outbursts, low-mass X-ray binaries demonstrate a complex behavior accompanied by a rapid change in their spectral and timing characteristics in the entire range of the electromagnetic spectrum — from radio to hard X-rays. So far there is no complete, self-consistent model describing all of the observed phenomena, including the rapid changes in visible and near-infrared fluxes and the correlation of these changes with the X-ray emission, while the observed evolution of outbursts is described in terms of the transition between characteristic states. Based on quasi-simultaneous optical, infrared, and X-ray observations, we show that the sharp decline in optical brightness near the low/hard-to-high/soft state transition is accompanied by an increase in the frequency of the observed X-ray quasi-periodic oscillations. This behavior can be explained in terms of the model in which both X-ray and optical emissions are produced by the synchrotron mechanism in a hot flow near a compact object.
      PubDate: 2021-12-01
       
  • Kinematic Properties of the GAIA EDR3 Catalogue

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      Abstract: We have obtained a solution of the Ogorodnikov–Milne stellar-kinematics equations based on the material of the entire Gaia EDR3 star catalogue containing 1.8 billion objects. In view of the insufficient accuracy of individual trigonometric parallaxes, we have also obtained an analogous solution based on a sub-catalogue of selected 98 million stars for which the parallaxes are known with an accuracy better than 1 \({\%}\) . We have performed a detailed analysis of these solutions as a function of stellar magnitude and distance.
      PubDate: 2021-12-01
       
  • Populations of Ultraluminous X-ray Sources in Galaxies: Origin and
           Evolution

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      Abstract: A model of the population of ultraluminous X-ray sources (ULXs) in binary systems with black hole (BH) accretors is constructed by hybrid population synthesis and is compared with the model of the population of ULXs with magnetized neutron stars (NSs) that can be observed as pulsating ULXs (Kuranov et al. 2020). A model of the formation of BHs whereby their mass is determined by the mass of the CO core immediately before its collapse ( \(M_{\mathrm{CO}}\) ) and ‘‘delayed’’ and ‘‘rapid’’ collapse models (Fryer et al. 2012) are considered. The possible transiency of ULXs due to accretion disk instability is taken into account. The parameters and evolution of ULXs in galaxies with a constant star formation rate (SFR) and in those with an old stellar population after an instantaneous star formation burst are computed. The maximum number of ULXs with BHs ( \({\sim}10\) ) is reached in galaxies with a stationary \(SFR=10M_{\odot}\) yr \({}^{-1}\)   \({\sim}1\) Gyr after the beginning of star formation. ULXs observed after the end of star formation are close binary systems in which BHs and/or NSs formed before the end of star formation, while long-lived donors with a mass \({\sim}M_{\odot}\) continue to overflow their Roche lobes after its end or have filled their Roche lobes even later. Several Gyr after the end of star formation the number of ULXs in galaxies with a mass \(M_{G}=10^{10}M_{\odot}\) is no more than 0.1, most of them are ULXs with NSs. Persistent sources with a Roche-lobe-overflowing optical star dominate in ULXs with NSs, irrespective of the adopted star formation model. The transient sources are an order of magnitude fewer. The ULXs accreting from the stellar wind of the optical component are an order of magnitude fewer than the sources with accretion via Roche lobe overflow.
      PubDate: 2021-12-01
       
  • Gamma-Ray Bursts: Multiwavelength Investigations and Models

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      Abstract: We present a brief history and the current status of research on gamma-ray bursts (GRBs), including observations at various GRB phases: the prompt emission, afterglow, supernova/kilonova, and the host galaxy. An overview of the known phenomenological features and theoretical models for GRBs is given. Problems, the solution of which is necessary for a successful study of the phenomenon of GRB, are discussed.
      PubDate: 2021-12-01
       
  • Transient AT2018cow: A Scenario with an Equatorial Disk

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      Abstract: To explain the presence of early X-ray emission from the object AT2018cow, we have studied a scenario with the presence of dense ejecta in the system in the equatorial plane. Based on a simplified one-dimensional model, we have developed a two-dimensional model with a dense equatorial disk in the system. As a result of two-dimensional radiation-hydrodynamics simulations with the multidimensional parallel FRONT code, we have shown that the shock wave propagates through such a disk more slowly than through the original low-density cloud and gives rise to a high-temperature region visible in X-rays in a certain range of viewing angles.
      PubDate: 2021-11-01
       
  • Orbits of Visual Double Stars from P. Couteau’s Catalogue Determined
           with Gaia DR2 and Gaia EDR3 Data

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      Abstract: The orbits of ten stars discovered by P. Couteau have been determined for the first time: COU 99, 357, 610, 850, 1346, 1531, 1642, 1752, 1845, and 2459. For two of them (COU 850 and 1752) an arc of more than half a revolution is covered by observations; the orbits of the remaining stars have been determined from short arcs ( \(5^{\circ}{-}50^{\circ}\) ). The orbits of COU 99, 610, 1346, 1531, and 1845 have been computed using the sums of the component masses estimated from photometric data and trigonometric parallaxes in the Gaia, Hipparcos, and Tycho catalogues. In addition, the orbits of COU 66, 169, 773, 1006, and 1897 have been improved.
      PubDate: 2021-11-01
       
  • On the Definition of the Astrocentric Coordinates in the Planetary Problem

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      Abstract: Two ways of defining the Poincaré astrocentric coordinates in the planetary problem are considered and compared. Both ways are shown to lead to the same system of equations of planetary motion after the elimination of the center of mass. Formulas for the transition from the osculating elements in the Poincaré coordinate system to the ordinary astrocentric osculating elements are given. The analytical apparatus constructed here is suitable for the practical application of perturbation methods, in particular, averaging methods.
      PubDate: 2021-11-01
       
  • Study of the Influence of the Background Neutral Component on the Dynamics
           of the Envelope in Supernova Remnants

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      Abstract: The influence of neutrals on the development of multidimensional dense-shell instabilities in supernova remnants is investigated. We present a model in which the neutrals are described as a permanently present additional medium (with its own parameters: temperature, density, velocity, etc.) that interacts with the ion component through collisional processes. Within this model we have found that the presence of neutrals suppresses the growth of instabilities in the case where they dominate in the total density of the medium.
      PubDate: 2021-11-01
       
  • Evolution of Planetary Chaotic Zones in Planetesimal Disks

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      Abstract: Extensive numerical experiments on the long-term dynamics of planetesimal disks with planets in systems of single stars have been carried out. The planetary chaotic zone clearing timescales \(T_{\mathrm{cl}}\) as a function of mass parameter \(\mu\) (planet–star mass ratio) have been determined numerically with a high accuracy separately for the outer and inner parts of the chaotic zone. Diffusional components \({\propto}\mu^{-6/7}\) and \({\propto}\mu^{-2}\) have been revealed in the dependence \(T_{\mathrm{cl}}(\mu)\) . The results obtained are discussed and interpreted in light of existing analytical theories based on the mean motion resonance overlap criterion and in comparison with previous numerical approaches to the problem.
      PubDate: 2021-11-01
       
  • TRGB Distances to Galaxies Based on Hubble Space Telescope (HST) Images in
           One F814W Filter1

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      Abstract: We analyze the reasons for imaging in the \(V\) and \(I\) filters to measure the distances to galaxies by the TRGB method. We show the possibility of using the TRGB method if Hubble Space Telescope (HST) images only in one F814W ( \(I\) ) filter are available. Based on archival HST images, we have carried out stellar photometry for 12 galaxies: NGC 1058, NGC 1365, NGC 1448, NGC 3079, NGC 3810, NGC 4321, NGC 4328, NGC 4485, NGC 4490, NGC 4651, NGC 6951, and NGC 7331, and measured their distances by the TRGB method. For many of the galaxies from this list such measurements have been made for the first time. A comparison of our results for galaxies with known TRGB measurements has shown good agreement.
      PubDate: 2021-11-01
       
  • Hydrodynamic Model of Decaying Radial Oscillations in RU Cam

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      Abstract: Calculations of stellar evolution up to the early white dwarf stage were carried out for stars with mass on the main sequence \(M_{0}=0.82\) , \(0.85\) , \(0.9M_{\odot}\) and with initial abundances of helium and heavier elements \(Y=0.25\) and \(Z=10^{-3}\) , respectively. For each value of \(M_{0}\) the AGB and post–AGB evolutionary phases were computed with three values of the mass loss parameter in the Blöcker formula: \(\eta_{\textrm{B}}=0.02\) , \(0.05\) , and \(0.1\) . The variable star RU Cam with pulsation period \(\Pi\approx 22\) day is shown to be in the post–AGB stage and the pulsation amplitude decrease in years 1962–1963 is due to movement of the star across the HR diagram beyond the pulsation instability region. Theoretical estimates of the mass and the luminosity of RU Cam are \(0.524\leq M\leq 0.532M_{\odot}\) and \(2.20\times 10^{3}\leq L\leq 2.33\times 10^{3}L_{\odot}\) , respectively. Hydrodynamic calculations of nonlinear stellar pulsations show that while the star approaches the instability boundary a significant reduction ( \({\approx}90\%\) ) in the pulsation amplitude occurs for nearly two years with subsequent slow decay of low–amplitude oscillations. Solution of the equations of hydrodynamics with time–dependent inner boundary conditions describing evolutionary changes in the radius and the luminosity at the bottom of the pulsating envelope allows us to conclude that decay of radial oscillations in RU Cam is accompanied by the effect of oscillation hysteresis. In particular, the stage of large–amplitude limit cycle oscillations extends by \({\approx}12\) yr and the subsequent stage of decaying small–amplitude oscilations spreads beyond the formal boundary of pulsation instability.
      PubDate: 2021-11-01
       
  • On a Possible Spicule Formation Mechanism in Quiet Regions of the Sun

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      Abstract: We consider the gravitational energy of the material falling from the corona as a source of energy for the formation of spicules in the solar chromosphere. We show that in the quiet chromosphere–corona transition region a downward-directed flow of material can generate an upward-traveling shock wave. Part of the energy of the falling material returns to the corona and contributes to its heating. We find the velocities of the falling material needed for this purpose. The corresponding range of velocities agrees well with present-day observations.
      PubDate: 2021-10-01
      DOI: 10.1134/S1063773721100030
       
  • Observations of Candidates for Eclipsing Cataclysmic Variables with the
           RTT-150 Telescope

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      Abstract: We present the results of our photometric and spectroscopic observations. We have studied four cataclysmic variable stars: 2XMM J183251.4-100106, MLS1809017 J224712+461815, MGAB-V330, and MGAB-V410. We have analyzed the observational data and determined the periods of the systems from our photometric data. The object MLS1809017 J224712+461815 has been classified as an SU UMa-type dwarf nova. The remaining three systems are eclipsing ones, with 2XMM J183251.4-100106 and MGAB-V410 showing signatures of polars. At the same time, for MGAB-V410 the orbital period \(P_{\textrm{orb}}=2\overset{\textrm{h}}{.}2\) falls into the period gap for cataclysmic variables.
      PubDate: 2021-10-01
      DOI: 10.1134/S1063773721100042
       
  • Determination of H II Region Metallicity in the Context of Estimating
           the Primordial Helium Abundance

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      Abstract: The primordial \({}^{4}\) He abundance (Y \({}_{p}\) ) is one of the key characteristics of Primordial Nucleosynthesis processes that occurred in the first minutes after the Big Bang. Its value depends on the baryon/photon ratio \(\eta\equiv n_{b}/n_{\gamma}\) , and is also sensitive to the relativistic degrees of freedom which affect the expansion rate of the Universe at the radiation-dominated era. At the moment, the most used method of the determination of Y \({}_{p}\) is the study of the metal deficient H II regions located in blue compact dwarf galaxies (BCDs). In this paper, we discuss in detail various methods of the determination of H II region metallicity in the context of Y \({}_{p}\) analyses. We show that some procedures used in the methods lead to biases in the metallicity estimates and underestimation of their uncertainties. We propose a modified method for the metallicity determination, as well as an additional criterion for selecting objects. We have selected 69 objects (26 objects with high quality spectra from the HeBCD+NIR database and 43 objects from the SDSS catalog), for which we estimate Y and O/H using the proposed method. We have estimated Y \({}_{p}=0.2470\pm 0.0020\) which is one of the most accurate estimates obtained up to date. Its comparison with the value Y \({}_{p}=0.2470\pm 0.0002\) obtained as a result of numerical modelling of Primordial Nucleosynthesis with the value of \(\Omega_{b}\) taken from the analysis of the CMB anisotropy (Planck mission), is an important tool for studying the self-consistency of the Standard cosmological model (a possible discrepancy between these estimates could be an indicator of a new physics). The application of the proposed method allows one to more correctly estimate Y \({}_{p}\) and the slope \(d\) Y/ \(d\) (O/H). Further analysis of the data from the SDSS catalog can significantly increase the statistics of objects for the regression analysis, which in turn can refine the Y \({}_{p}\) estimate.
      PubDate: 2021-10-01
      DOI: 10.1134/S1063773721100054
       
  • Magnetic Fields of Neutron Stars

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      Abstract: The birth function of neutron stars in magnetic field \(B\) is estimated for two models of the evolution of radio pulsars corresponding to different directions of evolution of the inclination angle of the magnetic axis to the rotation axis \(\chi\) (toward small angles \({\sim}0^{\circ}\) or angles close to \(90^{\circ}\) ). We show that for both models at magnetic fields \(B>10^{12}\) G it is a power law with a break near \(10^{13}\) G. At the same time, however, the number of born pulsars with a super-strong magnetic field \(B>10^{14}\) G in the first model turns out to be smaller than that in the second one by an order of magnitude.
      PubDate: 2021-10-01
      DOI: 10.1134/S1063773721100017
       
  • Orbital Maneuvering in the Vicinity of Collinear Libration Points Using
           Light Pressure Forces

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      Abstract: The controlled motion of a spacecraft with a solar sail in interplanetary space near the collinear libration points \(L_{1}\) and \(L_{2}\) of the Sun–Earth system is investigated. The equations of the circular restricted three-body problem and their modifications are used to describe the orbital motion. We present a technique for constructing the orbital motion control laws and provide an estimate of the controllability region when solving the problem of stabilization or long-term spacecraft keeping in the vicinity of \(L_{1}\) and \(L_{2}\) . This technique is based on the solution of the control problem for a linearized model of the equations of orbital motion and the transfer of results to the nonlinear case. Such a technique for the construction of control laws extends the possibilities both in solving the problems of motion stabilization and in solving the problems of maneuvering in the vicinity of a collinear libration point. We estimate the controllability region for a spacecraft with a solar sail and present the trajectories of possible spacecraft motion that are provided by the solar sail orientation when flying from the vicinity of a collinear libration point. It is in these regions of space that the light pressure force can have a significant efficiency due to the relatively small magnitude of the gravitational force. As an example, we consider a model of a spacecraft with a solar sail whose sail area-to-mass ratio corresponds to the spacecraft from the implemented IKAROS project and is less than that of the CubeSat spacecraft from the implemented LightSail-2 project by an order of magnitude.
      PubDate: 2021-10-01
      DOI: 10.1134/S1063773721100066
       
  • Optical Spectroscopy of Quasars Discovered by SRG/eROSITA with a 2.5-m
           Telescope at the Caucasus Mountain Observatory of SAI MSU

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      Abstract: Based on observations with the transient double-beam spectrograph (TDS) at the 2.5-m telescope of the Caucasus Mountain Observatory of SAI MSU, we have determined the redshifts for 15 new quasars detected in X-rays by the eROSITA telescope of the SRG orbital observatory during the first three all-sky surveys. The redshifts of the sources lie in the range 0.5–4.156. We have estimated the masses of the central supermassive black holes and the bolometric luminosities for eight quasars from the width of the C IV 1549 Å emission line and the continuum flux at 1350 Å. For these objects we have also estimated the ratio of the X-ray luminosity to the Eddington limit to be a few percent. At the same time, the bolometric-to-Eddington luminosity ratio for them has turned out to be in a fairly narrow range, 30–40 \({\%}\) . A large \(L_{\textrm{bol}}/L_{\textrm{Edd}}\) ratio points to an active growth of the mass of the central black holes in these objects.
      PubDate: 2021-10-01
      DOI: 10.1134/S1063773721100029
       
  • X-ray Observations of Historical Classical Nova Counterparts with eROSITA
           Telescope Onboard the SRG Orbital Observatory during the All-Sky Survey

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      Abstract: The X-ray emission from the counterparts of historical classical novae (CNe) in our Galaxy is studied. For this purpose, we use data from three SRG/eROSITA sky surveys in the half of the sky for the processing of which the Russian SRG/eROSITA consortium is responsible. Out of 309 historical CNe, X-ray emission has been detected from 52 sources with 0.3–2.3 keV luminosities \(L_{X}\approx 10^{30}\sim 10^{34}\) erg s \({}^{-1}\) . Among them, two sources with supersoft spectra are associated with the post-nova supersoft X-ray emission. X-ray spectroscopy suggests that systems with magnetized white dwarfs (WDs) may account for some fraction in our sample of CN counterparts detected in X-rays. This suggestion will be checked during further SRG/eROSITA sky surveys. The CN counterparts represent a bona fide sample of accreting WDs with non-steady thermonuclear hydrogen burning on their surface, while their X-ray luminosity in quiescence is a good indicator of the accretion rate in a binary system. Using this fact, we have constructed the accretion rate distribution of WDs with non-steady hydrogen burning and compared it with the accretion rate distribution of known steady supersoft X-ray sources in our Galaxy and nearby external galaxies. There is a pronounced dichotomy between these two distributions—the CN counterparts and the steady supersoft sources are in different regions, in accordance with the predictions of the theory of thermonuclear hydrogen burning on the WD surface.
      PubDate: 2021-09-01
      DOI: 10.1134/S1063773721090048
       
  • Three-Dimensional Kinematics of Classical Cepheids

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      Abstract: A linear Ogorodnikov–Milne model is applied to study the three-dimensional kinematics of classical Cepheids in the Milky Way. A sample of 832 classical Cepheids from Mróz et al. (2019) with distances, line-of-sight velocities, and proper motions from the Gaia DR2 catalogue is used. The Cepheid space velocities have been freed from the differential Galactic rotation found by us previously based on a nonlinear rotation model. Based on a complete Ogorodnikov–Milne model, involving the line-of-sight velocities and proper motions of stars, we have estimated the angular velocity of rotation around the Galactic \(y\) axis, \(\Omega_{y}=0.64\pm 0.17\) km s \({}^{-1}\) kpc \({}^{-1}\) . We think that this rotation is associated with the warp of the Galactic thin disk. Our calculations using only the proper motions of Cepheids under the assumption of no deformations due to the disk warp have shown the presence of a residual rotation around the \(y\) axis with an angular velocity \(\Omega_{y}=0.54\pm 0.15\) km s \({}^{-1}\) kpc \({}^{-1}\) and the presence of a positive rotation around the \(x\) axis with an angular velocity \(\Omega_{x}=0.33\pm 0.10\) km s \({}^{-1}\) kpc \({}^{-1}\) .
      PubDate: 2021-09-01
      DOI: 10.1134/S1063773721090012
       
  • Host Stars of Planets on the Hertzsprung–Russell Diagram

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      Abstract: Our statistical analysis (based on Kolmogorov–Smirnov tests) of the mass and radius distributions of planets hosted by stars of different classes reveals their significant differences, depending on the class of host stars. These differences can be explained by (1) the long-term dynamical evolution of planetary systems, (2) the long-term physical evolution of host stars, and (3) the initial differences in the structure of systems. Kolmogorov–Smirnov tests show at a high significance level that during the transition of a star from the main sequence to the red giant branch its planetary system disintegrates, at least partially. We provide estimates of the dynamical disintegration timescale for various architectures of planetary systems. From a comparison of the estimates of the physical and dynamical evolution timescales we have concluded that the disintegration of the inner regions of planetary systems is mainly physical (absorption by the stellar atmosphere) rather than dynamical (breakup within the N-body problem) in nature. As regards the outer parts of planetary systems, their disintegration can be both purely dynamical (intrinsic disintegration, close encounters with neighboring stars) and mixed physical–dynamical (i.e., the physical destruction of the system’s inner component can trigger a dynamical breakup of the outer part) in nature.
      PubDate: 2021-09-01
      DOI: 10.1134/S1063773721080016
       
 
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