Vol 62, No 12 (2018)

Most of the energy released in the gravitational collapse of the cores of massive stars is carried away by neutrinos. Neutrinos play a pivotal role in explaining core-collapse supernovae. In this work the multidimensional gas dynamics is used with neutrino transport in the flux-limited diffusion approximation to study the role of multi-dimensional effects. The possibility of large-scale convection is discussed, which is interesting both for explaining SNII and for setting up observations to register possible high-energy (≲10 MeV) neutrinos from the supernova. In compare with the previous work describing a new multidimensional gas dynamics method with neutrino transport we investigate the role of the rotation in the convection.

In this work, cold and hot, static and rotating white dwarf stars are investigated within the framework of classical physics, employing the Chandrasekhar equation of state. The main parameters of white dwarfs such as the central density, pressure, total mass and radius are calculated fulfilling the stability criteria for hot rotating stars. To construct rotating configurations the Hartle approach is involved. It is shown that the effects of finite temperatures become crucial in low-mass white dwarfs, whereas rotation is relevant in all mass range. The simultaneous accounting for temperature and rotation is critical in the calculation of the radii of white dwarfs. The results obtained in this work can be applied to explain a variety of observational data for white dwarfs from the Sloan Digital Sky Survey Data Releases.

We analyze four high resolution rich samples of Ly-α and metal lines (two at z ≥ 2 and two at z ≤ 0.2). We describe evolution of the observed Doppler parameters and absorbers separation and propose a model of the forest. We argue that all absorption lines are formed in gaseous caustics created in stable DM subclouds. The absorption lines are described by two local characteristics, the Doppler parameter and the column density of neutral hydrogen. We show that evolution of the Doppler parameter is very slow and its mean value increases by a factor ≤1.5 at redshifts 0 ≤ z ≤ 3. We show that absorbers separation increases as <d_sep ∝ (1 + z)−2. We describe evolution of absorbers in the framework of a two component model: the first population represents absorbers with just one line created in compact stable DM clouds with random spatial distribution, and the second population includes absorbers with two, three and more absorption lines formed in more massive and extended random DM clouds. Slow evolution of the Doppler parameter indicates high stability of caustics and conditions within clouds. For absorbers of the second population relative velocity of lines slowly increases with time.

Geons are localized horizonless objects formed by gravitational waves, held together by the gravitational attraction of their own field energy. In many respects they are similar to scalar field pulson/oscillon configurations, which were found numerically in 1976 by Kudryavtsev, Bogolyubskii, and Makhankov. If there is a negative cosmological constant, the spacetime of geons asymptotically approaches the anti-de Sitter (AdS) metric. AdS geons are time-periodic regular localized vacuum solutions without any radiation loss at infinity. A higher order perturbative construction in terms of an amplitude parameter shows that there are one-parameter families of AdS geon solutions emerging from combinations of identical-frequency linear modes of the system.

We determine the possible gravitational wave polarizations in two general classes of teleparallel gravity theories, using the metric and symmetric teleparallel geometries. For this purpose we apply the Newman–Penrose formalism, and find that depending on the choice of parameters, the E(2) class of the theories is one of N₂,N₃, III₅, II₆, corresponding to two to six polarizations, where all of them include the two tensor polarizations known from general relativity. We also find classes of theories apart from general relativity which yield the same polarizations.

In this work we study a role of baryon load and interstellarmediumdensity to explain the nature of peaks in the ultra-relativistic prompt emission (UPE) phase of Gamma-ray Bursts (GRBs). We study the behavior of their Γ Lorenz factor fromthe moment of transparency all the way up to interstellarmedium. We finally study the characteristic of equitemporal surfaces in the UPE phase.

Measuring time delays from strongly lensed supernovae (SNe) is emerging as a novel and independent tool for estimating the Hubble constant (H₀). This is very important given the recent discord in the value of H₀) from two methods that probe different distance ranges. The success of this technique will rely of our ability to discover strongly lensed SNe with measurable time delays. Here, we present the magnifications and the time delays for the multiply-imaged galaxies behind the Hubble Frontier Fields (HFF) galaxy clusters, by using recently published lensing models. Continuing on our previous work done for Abell 1689 (A1689) and Abell 370, we also show the prospects of observing strongly lensed SNe behind the HFF clusters with the upcoming James Webb Space Telescope (JWST). With four 1-hour visits in one year, the summed expectations of all six HFF clusters are ~0.5 core-collapse (CC) SNe and 0.06 Type Ia SNe (SNe Ia) in F115W band, while with F150W the expectations are higher, ~0.9 CC SNe and ~0.06 SNe Ia. These estimates match those expected by only surveying A1689, proving that the performance of A1689 as gravitational telescope is superior. In the five HFF clusters presented here, we find that F150W will be able to detect SNe Ia (SNe IIP) exploding in 93 (80) pairsmultiply-imaged galaxies with time delays of less than 5 years.

Long gamma-ray burst GRB 151027A was observed by all three detectors onboard the Swift spacecraft, and many more, including MAXI, Konus-Wind and Fermi GBM/LAT instruments. This revealed a complex structure of the prompt and afterglow emission, consisting of a double-peak gammaray prompt with a quiescent period and a HRF/SXF within the X-ray afterglow, together with multiple BB components seen within the time-resolved spectral analysis. These features, within the fireshell model, are interpreted as the manifestation of the same physical process viewed at different angles with respect to the HN ejecta. Here we present the time-resolved and time-integrated spectral analysis used to determine the energy of the e⁻e⁺ plasma E_tot and the baryon load B. These quantities describe the dynamics of the fireshell up to the transparency point. We proceed with the light-curve simulation from which CBM density values and its inhomogeneities are deduced. We also investigate the properties of GRB 140206A, whose prompt emission exhibits a similar structure.

By applying a parabolic–hyperbolic formulation of the constraints and superposing Kerr–Schild black holes, a simple method is introduced to initialize time evolution of binary systems. As the input parameters are essentially the same as those used in the post-Newtonian (PN) setup the proposed method interrelates various physical expressions applied in PN and in fully relativistic formulations. The global ADMcharges are also determined by the input parameters, and no use of boundary conditions in the strong field regime is made.

The conference “Modern Astrometry 2017,” which took place on Octobr 23–25, 2017 at the Sternberg Astronomical Institute of Lomonosov Moscow State University, was dedicated to the memory of the eminent astrometrist, teacher, and outstanding scientist and Doctor of Physical–Mathematical Siences Konstantin Vladslavovich Kuimov, who worked at the Sternberg Astronomical Institute during 1962–2017. This article is based on a presentation made at this conference.

There is wide interest in the results of studies of the dynamics of satellites of planets. Such data are needed to determine the physical properties of celestial bodies, and they may be able to provide information about the origins and evolution of the solar system. The general approach to studying the dynamics of satellites involves developing models for the motion and ephemerides based on observational data. Ephemerides are required to prepare and launch space missions to other planets and help discover new celestial bodies. High-precision astrometric coordinates of the principal satellites of Jupiter, Saturn, and Uranus are derived from photometric observations of occultations and eclipses of these satellites. To this end, worldwide observing campaigns have been organized. Enhancement in the precision of ephemerides can be obtained not only by increasing the accuracy of observations, but also by expanding the time interval covered by the observations. Many new, distant satellites of the major planets were discovered in the early 21st century. However, observations of these satellites are scarce and were obtained over short time intervals; as a result, some of these satellites were lost. To date, 179 natural satellites are known. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

The main aim of this paper is to survey main trends in creating modern sources of astrometric and photometric data in astronomy. A list of existing optical, IR, and UV surveys and other surveys whose release is planned for the near future is given, together with a brief description and comparative analysis. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute,Moscow State University, October 23–25, 2017).

A review of the achievements of space geodesy in the 21st century, represented by the successful realization of the CHAMP, GOCE, and GRACE missions, is presented. The main result of these missions is the creation of models for the gravitational field of the Earth with high spatial and temporal resolution. In particular, for an uncertainty in the height of the geoid of ~1 mm, the monthly models contain about 50 spherical harmonics, corresponding to a spatial resolution of ~400 km. The GRACE Follow On mission was launched inMay 2018, whose aim is to provide data for the monthly global models for the gravitational field of the Earth initiated with the GRACE mission. Paths for the development of the next generation of space gravimetry projects are considered. These will enable an appreciable (by no less than a factor of 10) improvement in the precision of models for the gravitational field of the Earth. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

A number of questions about the Moon remain to be answered, including fundamental questions related to the internal structure and origin of the Moon. Studies of the spin–orbital dynamics of the Moon and of selenodesy are required for the practical solution of a number of problems related to navigation on the Moon and in circumlunar space, with the aim of providing coordinate and time support for planned lunar space projects. This paper analyzes existing dynamic selenographic reference grids, considers methods for their development and creation, and describes the modern projects related to navigational support for lunar missions. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

It has recently become clear that the potential role of astrometry in cosmological studies has been underestimated. Some areas of cosmology that should be investigated using astrometrical methods are discussed. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

Results of studies of relativistic effects for the time and frequency shifts for an Earth–satellite system of atomic clocks, and also for moving clocks on the Earth, are presented. In addition to the known solutions, the influence of the irregular rotation of the Earth and of the fields of the Moon and Sun on ground and satellite clocks are included, as well as the influence of a number of other perturbing factors that are difficult to take into account (atmospheric resistance, solar radiation pressure, the albedo of the Earth, etc.). The concept of a near-Earth “gravitational sphere,” characterized by the relativistic index of refraction and the gravitational coefficient for the transformation of frequencies, is introduced for computations of relativistic effects along space radio-wave propagation pathways. Applications for methods of relativisticmetrology are proposed. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

A catalogue of variable stars in the constellation Cepheus has been composed in the course of work on Version 5.1 of the General Catalogue of Variable Stars (GCVS). A brief description of work on the catalogue is presented, together with tables from Version 5.1 of the GCVS for variable stars in this constellation. The catalogue contains 1018 stars.