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: 178)
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 AstronomĂ­a y AstrofĂ­sica     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: 192)
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
Astrophysics
Journal Prestige (SJR): 0.225
Number of Followers: 29  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1573-8191 - ISSN (Online) 0571-7256
Published by Springer-Verlag Homepage  [2626 journals]
  • Spectroscopy and Kinematics of the High-Latitude UX Ori Type Star V1117
           Her
    • Abstract: Results from a study of low resolution spectra and kinematics of the star V1117 Her located at a high galactic latitude b = +33°.8 are presented. It is shown that this star has A7 IV photospheric class, luminosity L ≈ 26 Lʘ, and spectral signs of accretion activity. This confirms its previous classification as a young Ae Herbig star with photometric UX Ori type variability. In addition, the parallax of V1117 Her in the GAIA DR2 catalog corresponds to a distance of D ≈ 1.4 kpc to it, which represents a height Z ≈ 800 pc of the star above the galactic plane. Here the kinetics of the star indicates its more probable formation in situ, outside the plane of the young disk. A possible scenario for the formation of V1117 Her is discussed briefly.
      PubDate: 2020-11-17
       
  • Barometric Formula for Ultrarelativistic Degenerate Fermi-Gases
    • Abstract: An exact explicit barometric formula is derived for an ultrarelativistic degenerate Fermi-gas governed by the Chandrasekhar equation of state.
      PubDate: 2020-11-14
       
  • Outburst of V1118 Ori during 2018-2020
    • Abstract: New observational data on the last two outbursts of the EXor star V1118 Ori are presented. The combined light curve of the last outburst is derived and fitted. The dates of the start of the outburst, its maximum, and end, as well as the maximum magnitude, and the rates of increase and decrease of the brightness were determined.
      PubDate: 2020-11-14
       
  • Fundamental Reasons for the Similarity and Differences of the Mass Spectra
           of Various Astronomical Objects
    • Abstract: The mass spectra of astronomical objects of various kinds are compared: cosmic dust, asteroids, planets, stars, star clusters, galaxies, and galactic clusters. The authors have previously noted a similarity in the (initial) mass functions for relatively massive objects (stars, galaxies, galactic clusters). In this paper the range of masses of astronomical objects is extended to the limit and covers roughly 68 orders of magnitude. It is confirmed that the initial mass spectra of objects in ensembles formed by fragmentation (a fast process) may, in a first approximation in a statistically significant range be represented by a basis (reference) function dN / dM ∞ M-2, where dN is the number of objects in a range [M, M+dM] of masses. The significance of this function is the probability density of formation of objects, which total mass in a range [d ln M] of masses is independent of the mass M or, in other words, reduces to the absence of a distinct mass scale. The physical reasons determining the deviation of the initial mass functions from the reference function are discussed briefly. It is noted that the mass spectra in ensembles of objects formed by mergers (coagulation in the case of dust), i.e., in a relatively slow evolutionary process, can also be of a form close a reference function. The main reason for this universality lies in the random character of the processes of formation and evolution of these ensembles of astronomical objects.
      PubDate: 2020-11-14
       
  • PPN Motion of S-Stars Around Sgr A*
    • Abstract: The equations of motion for the parametrized post-Newtonian (PPN) formalism for several S-stars close to the relativistic compact object Sgr A* at the center of the galaxy are examined. The effect of the difference in the periods of Newtonian and post-Newtonian orbits is taken into account. The period of the best approximation to the PN-orbit of the star S2 exceeds the period of the Newtonian orbit by 16 days. The PPN parameters βPPN and γPPN are measured. Bayesian methods are used for fitting the trajectories of the PPN motion. Posterior estimates of βPPN and γPPN \( {0.97}_{-0.65}^{+0.42} \) and \( {0.81}_{-0.60}^{+0.46} \) are obtained, respectively. This result confirms the prediction of the general theory of relativity for the post-Newtonian equations of motion under conditions close to Sgr A*.
      PubDate: 2020-11-14
       
  • Spectral Observations of Emission Stars in the Vicinity of Cyg OB7
    • Abstract: Results from spectral observations of known emission stars in the vicinity of Cyg OB7 are presented. 64 spectra of 9 emission stars were obtained over the period 2001-2007. The equivalent widths of the most characteristic lines for T-Tau stars were obtained in all these spectra. It is noted that all the spectral lines manifest strong variations. The spectra of these stars are in the spectral range K8-M4. Two stars (Nos. 12 and 23) have a negative Balmer jump. The forbidden [OIII] 4959 and 5007 Å and [SII] 6716/31 Å lines, which are typical of classical T-Tau stars, show up in the spectra of stars No. 23 and 86.
      PubDate: 2020-11-14
       
  • Differential Rotation of Stars in Spectral Class A
    • Abstract: Published data indicate a substantial increase in the differential rotation parameter ∆Ω of stars hotter than 6700 K. By analyzing the shape of the light curves and the presence of a specific set of peaks in their power spectra, we have found that 47 of 57 objects with Teff greater than 7500 K that were studied can be identified as pulsating stars and only 10, as stars with brightness variation owing to rotational modulation. After eliminating the pulsating variables, for the stars with Teff greater than 7500 K the average value of ∆Ω= 0.051±0.01 rad/day. This conclusion conflicts with our earlier assumption that the peaks in the power spectra for ROTD stars are caused by a possible manifestation of differential rotation. Further independent evidence for a low value of ∆Ω for stars in spectral class A has been obtained from Zeeman-Doppler charts for the star γ Gem, with an estimate for the differential rotation parameter of the star of 0.0073±0.0023 rad/day.
      PubDate: 2020-11-14
       
  • Analytic Solution of the Nonlinear Radiative Diffusion Problem in a
           One-Dimensional Purely Scattering Medium. II
    • Abstract: This paper is the second part of the author’s previous work. Its purpose is to illustrate the efficiency of using the previously introduced auxiliary functions known as linear images (LI) of the reflection-transmission function with simple examples of nonlinear problems for a one-dimensional purely scattering medium. First, an explicit analytic solution is obtained for the nonlinear “direct” problem of determining the fields of the emerging radiation from a “composite” medium consisting of a reflecting surface and a layer of finite thickness with known reflecting-transmitting properties. Then solutions are obtained for the nonlinear “inverse” problems of determining: (a) the external exciting fields based on data from the radiation emerging from the medium, (b) the fields at an “inaccessible” boundary of the medium based on observations of the light regime at one of its boundaries, (c) the intensities of the radiation traveling in one direction based on measurements of the fields in the opposite direction, (d) some characteristics of the medium based on measurements of the intensities of radiation incident on it from outside and emerging through one of its boundaries, and (e) fields inside the medium based on measurements of the bidirectional radiation fields at just one boundary of the medium. Finally, it is shown that in the nonlinear problem of illumination of an semi-infinite medium the phenomenon of “bleaching” of the medium does not occur; the light regime coincides with the solution of the linear problem, both outside and inside the medium.
      PubDate: 2020-11-14
       
  • Some Manifestations of Nonstationarity in the Spectra of Early-Type
           Supergiants
    • Abstract: This is a theoretical study of changes in several characteristics of the spectra of early-type supergiants owing to scattering of continuum radiation. Thomson scattering on free electrons is treated as the scattering mechanism, although the approach used here is quite general. The reason for changes in the spectral class of a star with constant bolometric luminosity and surface temperature is elucidated and the necessary conditions for their realization are introduced. The effect of scattering in the continuum on the magnitude of the intensity jumps in the hydrogen spectrum depending on the degree of ionization is studied. The conditions under which the Schuster mechanism for formation of emission lines sets in are clarified both for an isothermal atmosphere and for an atmosphere with a temperature gradient.
      PubDate: 2020-11-14
       
  • A Multiwavelength Study of Distant Blazar PKS 0537-286
    • Abstract: We report the results of broadband observations of distant blazar PKS 0537-286 (z = 3.1) using data spanning more than ten years from the Fermi Large Area Telescope together with Swift UVOT/XRT archival data taken between 2005 and 2017. In the γ -ray band, the peak flux above 100 MeV, Fγ = (6 23 ± 0 56) ∙ 10-7 photon cm-2 s-1 observed on MJD 57874 within one week, corresponds to Lγ = 2 46 ∙ 1049 erg s-1 isotropic γ -ray luminosity. The Swift XRT data analyses show that the X-ray emission is characterized by a significantly hard photon index, ΓX-ray ≤ 1.3 , and an X-ray flux of 4 ∙ 10-12 erg cm-2 s-1, which is almost constant over twelve years. The spectral energy distribution is modeled within one-zone leptonic models assuming the emission region is within the broad-line region. The observed X-ray and γ -ray data are modeled as inverse Compton scattering of (i) only synchrotron photons and (ii) synchrotron and external photons on the electron population that produces the radioto-optical emission. The modeling shows that the nonthermal electrons in the jet of PKS 0537-286 have a hard power-law index (<1.9) and that the jet should be particle dominated with a luminosity within 1045-1046 erg s-1.
      PubDate: 2020-11-14
       
  • Study of the Binary Star ADS 7251 by Observations on the 65-cm Refractor
           at Pulkovo from 1962-2018
    • Abstract: Results are presented from a study of the binary star ADS 7251 (STF 1321) based on a uniform series of observations on the 65-cm refractor at Pulkovo from 1962 through 2018. The errors in the yearly average positions ρ and θ are equal to 0′′.004 and 0°.02 for the photographic and 0.”003 and 0.°01 for the CCD observations. A new orbit is calculated from the found relative position and the exact parallax of Gaia. The comparisons use modern observations of Hipparcos and Gaia, as well as observations from the distant past in the nineteenth century by Struve. This study yielded better convergence with the distant observations when the Gaia parallax was used. The errors calculated from O-C are 0′′.008 ÷ 0′′.011 . They are comparable to those obtained for other binary stars close to the sun, as well as to the corresponding estimates for stars rotating around the central body of the galaxy and observed on the Keck and VLT telescopes. The importance of observations of the components A and B of ADS 7251 as possible parent stars for exoplanets is noted.
      PubDate: 2020-11-14
       
  • Humps and Superhumps in the SU UMa-Type Dwarf Nova System IRXS
           J161659.5+620014
    • Abstract: Photometric studies of the SU UMa-type dwarf nova IRXS J161659.5+620014 have been made on the 2.6-m and 1.25-m telescopes at the Crimean Astrophysical Observatory during 2017 and 2018 in the quiescent state of the system, during normal outbursts, and during superoutbursts. It is found that the interval between adjacent normal outbursts was about 11 days during 2017. Observations in the quiescent state during 2017 yielded an orbital period of 0.06888(2) days. Observations during 2018 manifested good reproducibility of the characteristics of the superoutbursts compared to those of previous years. A refined period of 0.071044(15) days was obtained for the positive superhumps in stage “C” and their color indices were determined.
      PubDate: 2020-11-14
       
  • On the Alignment of Galaxies in Clusters
    • Abstract: We explore the distribution of position angles (PA) of galaxies in clusters. We selected for study the isolated clusters, since the distribution of the galaxy orientation in clusters with close neighbors could be altered by the gravitational influence of the latter. We assume that galaxies are aligned, if their number at one 90º position angle interval is more than twice higher than at the other 90º interval. We study the galaxy PA distribution at the outer regions of clusters with smaller space density, where the probability of the PA variation in the result of interactions between galaxies is smaller than at the dense central regions. We found that the alignment of galaxies is more often observed in poor clusters and concluded that originally galaxies were aligned, but in the result of accretion in time of field galaxies with arbitrary orientations and also due to the mutual interactions the relative number of aligned galaxies decreases.
      PubDate: 2020-11-11
       
  • Secular Stability of the Magnetic Structures of Magnetic Stars. II
    • Abstract: Numerous indications that the magnetic field structures in magnetic stars do not change with age are cited. The stars rotate like a solid.
      PubDate: 2020-09-12
       
  • Photometric and Spectral Study of the Be/X-Ray Binary Object V725
           Tau=A0535+262
    • Abstract: This is a study of spectral and photometric observations of the binary system with an X-ray component V725 Tauri=A0535+262. It consists of a giant star HDE 245770 of spectral class O9.7 and the pulsar A0535+26 with a pulsation period of ~103 s. Active stages of this object, accompanied by “giant” X-ray outbursts, have been observed repeatedly. The last events occurred during 2009-2011. Our studies in 2017-2020 yielded the following data: over the last three years the B and V band brightness of the object has remained at a high level and began to decrease at the end of 2019. Here, beginning in 2016 a gradual increase in the radiative fluxes in the Hβ and Hα emission lines has been observed. At present the equivalent widths of these lines exceed the values recorded during the time of the gigan X-ray outburst of 2011. Previous studies have shown that a similar combination of the characteristics of this object, specifically an increase in emission line fluxes as the brightness decreases. is detected just before the onset of an active stage.
      PubDate: 2020-09-12
       
  • Classification by Activity Type of a Sample of Active Galaxies with Radio
           Emission
    • Abstract: This is a detailed spectral classification of 96 active galaxies from the Véron-Cetty and Véron catalog (2010, Version 13, VCV-13) of active galaxies and quasars. These objects were identified as radio sources using standard radio catalogs. Those galaxies which had radio sources in at least 6 different radio bands and had been identified spectrally in the SDSS catalog were selected. The types of activity of these were determined using their SDSS spectra. Three diagnostic diagrams and a direct study of the spectra were used for more certain classification. As a result, the classifications of 85% of the objects were changed. The radio sources in different radio bands make it possible to construct the spectral distribution of the energy in the radio range and to compare it with the optical activity types.
      PubDate: 2020-09-10
       
  • Slowly Rotating Ap Stars, Prospects for Observing Them with the Tess Space
           Mission
    • Abstract: The feasibility of detecting candidate slow-rotating magnetic Ap stars with periods from a few tens of days to several hundred years is considered. The question of the fraction of objects of this kind among all Ap stars is important from the standpoint of understanding the origin and evolution of magnetic stars. The search for such objects can be based on analysis of their photometric variability using observations from the TESS space mission. For this purpose, it is first planned to examine all the objects from the corresponding catalogs. It is shown how the proposed method may be used for the example of the slowrotating Ap star HD 50169, with a detailed analysis of its variability and for which observations from the TESS mission are already available.
      PubDate: 2020-09-09
       
  • Physical Conditions in Coronal Holes
    • Abstract: The physical conditions in the chromosphere of polar and equatorial coronal holes in the decay phase of the 24-th solar activity cycle are studied. Models of the chromosphere are constructed based on the intensities of the HeI 10830 Å and Hα lines and using a non-LTE program. The calculations showed that the temperature in equatorial coronal holes is similar to that of polar coronal holes. The temperature in coronal holes is lower than that of the unperturbed chromosphere and increases depending on height in the chromosphere. The difference between the atmospheres of coronal holes and the quiet Sun begins at the level of the upper photosphere- lower chromosphere.
      PubDate: 2020-09-09
       
  • Relationship of Coronal Holes at Mid and Low Latitudes to the Mean
           Magnetic Field of the Sun
    • Abstract: The relationship between the magnetic fluxes and areas of coronal holes (CH) at mid and low latitudes φ < 60° and the mean magnetic field (MMF) of the sun over the period from January 19 through December 12, 2012, is studied using ultraviolet images and magnetograms obtained with the Solar Dynamics Observatory satellite. It is shown that the boundaries of the CH determined with the algorithms CHIMERA (https://solarmonitor.org) and SPoCA (https://helioviewer.org) differ significantly. The correlation coefficient between the weighted total area of CHs taking into account the magnetic field polarity and MMF are in the range from 0.82 to 0.88. The CH can make a substantial contribution to the MMF since their fields have an open configuration and are not balanced on the solar disk. In light of the solar dynamo theory and the results obtained here, the annual time delays between the maxima of the Wolf numbers and the values of the MMF are discussed.
      PubDate: 2020-09-09
       
  • Regular and Oscillatory Motion of Coronal Bright Points
    • Abstract: Long-term automatic tracking of coronal bright points has made it possible to study their proper motions using data from the AIA 193 Å channel of SDO/AIA. Fits files for 95 visually long-lived bright points uniformly distributed in latitude have been chosen for processing. A specially developed program automatically fixes the heliographic coordinates of the centroid of the chosen coronal bright points in a series of Fits files. It was found that the proper motions of all the coronal bright points studied here have a distinct oscillatory character. The periods of the oscillations range from 5 to 60 h with an average of 20 h. Some tendencies in the latitudinal dependence of the oscillatory characteristics have been found. A possible explanation of these oscillations in terms of the propagation of helical waves along the magnetic loops that form the structure of the coronal bright points is pointed out. Linear trends in the latitudinal and longitudinal components of the motion of the coronal points are used to determine the rotational velocity and meridional migration of the coronal bright points. An analysis of the rotational velocities confirms the differential character of the latitudinal dependence. The problem of determining the direction and magnitude of the meridional migration is discussed.
      PubDate: 2020-09-09
       
 
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