Detection of gravitational waves from astrophysical sources

Modern ground-based gravitational-wave antennas designed to detect bursts of gravitational radiation from astrophysical catastrophes are described. Basic antenna characteristics, peculiarities of the noise background in antennas from various sources, and methods of their suppression are presented. The contribution from cosmic rays to the background is estimated. New programs of searching for low-frequency gravitational waves and potentialities for increasing the sensitivity of antennas of new types are briefly described.     

Proposed searches for candidate sources of gravitational waves in a nearby core-collapse supernova survey

Gravitational wave bursts in the formation of neutron stars and black holes in energetic core-collapse supernovae (CC-SNe) are of potential interest to LIGO-Virgo and KAGRA. Events nearby are readily discovered using moderately sized telescopes. CC-SNe are competitive with mergers of neutron stars and black holes, if the fraction producing an energetic output in gravitational waves exceeds about 1%. This opportunity motivates the design of a novel Sejong University Core-CollapsE Supernova Survey (SUCCESS), to provide triggers for follow-up searches for gravitational waves. It is based on the 76 cm Sejong university telescope (SUT) for weekly monitoring of nearby star-forming galaxies, i.e., M51, M81-M82 and blue dwarf galaxies from the unified nearby galaxy catalog with an expected yield of a few hundred per year. Optical light curves will be resolved for the true time-of-onset for probes of gravitational waves by broadband time-sliced matched filtering.     

Intensity of gravitational wave emitted by an oscillating Keplerian binary

This paper attempts to formulate a way for calculating the intensity of gravitational wave from two point masses in Keplerian circular and elliptic orbits. The intensity is calculated with the assumption that the orbital plane of the binary undergoes small oscillation about the equilibrium x-y plane. This problem is simplification of a physically possible orbit where one of the point masses is spinning whereby the spin-orbit force drives the orbital plane to wobble in a complicated manner. It is shown that the total energy of gravitational wave emitted by the binary in this case is dominated by the parameters which take into account the oscillation of the plane. The results presented are in fact a generalization of the classic results of Landau and Lifshitz.     

The generation of high-frequency gravitational waves in a perfect fluid

The problem of the generation of a gravitational wave by an acoustic one is studied in the high-frequency domain for a perfect fluid. The negative result which is found may be of some relevance for astrophysical and cosmological applications.     

Modulational instability of fast magnetosonic waves emitted from a pinching current sheet

We investigate how fast magnetosonic waves can be produced from a pinching current sheet, by using 3-D MHD code. We show that after magnetic pinch of the current sheet due to pressure imbalance, the current sheet begins to expand by an excess of plasma pressure at the center of the current sheet. During the expansion phase, strong fast magnetosonic waves can be created at the steep region of the density gradient and propagate away from the current sheet. It is shown that the fast magnetosonic waves become unstable against modulational instability, as found by Sakai (1983). After the emission of the fast magnetosonic waves, the current sheet will relax to a new equilibrium state, where the current sheet can be heated by adiabatic compression. The emission processes of the fast magnetosonic waves from the current sheet, as well as the modulational instability of these waves that can lead to effective plasma heating through the Landau damping of the slow waves, are important for an understanding of coronal heating and coronal transient brightening.     

引力波引起的脉冲星计时残差模拟与分析

为了能将引力波引起的脉冲星计时残差从总的脉冲星计时残差中分离出来,我们介绍了3种形式的引力波(单一持续的引力波、单一瞬时的引力波和随机引力波背景)及其对脉冲星计时残差的影响,并利用脉冲星计时处理软件Tempo2进行了模拟,对模拟得到的这三种引力波源引起的脉冲星计时残差进行了分析比较。该工作在脉冲星时间尺度的建立及其应用方面具有参考意义。     

Emission of gravitational waves in the scalar-tensor theory of gravitation

Erevan State University. Translated from Astrofizika, Vol. 36, No. 3, pp. 323–430, July–September, 1993.     

Observational manifestations and intrinsic properties of the RCR sources in terms of a unified model

We present a summary results of the study of radio sources showing significant variations of integral flux density using the data from the RATAN-600 surveys of 1980–1994 at a frequency of 7.6 cm. The majority of the detected variable sources have flat radio spectra, although there are also all other spectrum types found. Point and compact sources predominate, although all known morphological structures are found in the sample. Variability is detected both in quasars and galaxies. Using the catalog data, we found brightness variations in the optical and/or infrared ranges for a half of host objects of radio sources. We analyzed the properties of nonvariable and variable RCR sources. We compared the ratio of absolute magnitude to radio luminosity for sources with the active nucleus types determined from the optical data. It is found that this parameter is approximately the same for quasars with different radio luminosity. It isminimum for the strongest radio galaxies and grows up to the level characteristic of quasars with the decrease of radio luminosity. Considering that the ratio depends on obscuring properties of a dust torus, such behavior can be explained if we assume that the torus geometry and its optical depth depend on the source long. This parameter is slightly higher among variable sources than among nonvariable ones which counts in favor of the nucleus more open to an observer.     

Simulation of a population of isolated neutron stars evolving through the emission of gravitational waves

We study, via a Monte Carlo simulation, a population of isolated asymmetric neutron stars where the magnitude of the magnetic field is low enough so that the dynamical evolution is dominated by the emission of gravitational waves. A starting population, with age uniformly distributed back to 100 Myr (or 500 Myr) and endowed with a birth kick velocity, is evolved in the Galactic gravitational potential to the present time. In describing the initial spatial distribution, the Gould belt, with an enhanced neutron star formation rate, is taken into account. Different models for the initial period distribution are considered. The star ellipticity, measuring the amount of deformation, is drawn from an exponential distribution. We estimate the detectability of the emitted gravitational signals by the first and planned second generation of interferometric detectors. Results are parametrized by the fraction of the whole galactic neutron star population made up of these kinds of sources. Some possible mechanisms, which would make possible the existence of such a population, are discussed. A comparison of the gravitational spin-down with the braking due to a possible interaction of the neutron star with the interstellar medium is also presented.     

On the nature of internal gravitational waves observed from hydroxyl emission

New data are given on internal gravitational waves observed from hydroxyl emission. The source of these waves is seen in certain sections of the jet stream excited by active meteorological formations lying beneath them.     

Thermodynamics of a model of nonadiabatic spherical gravitational collapse

In this work, a thermodynamic treatment of a Friedmann-like model of nonadiabatic spherical gravitational collapse is presented. The calculations have been performed according to Eckart's theory of dissipative relativistic fluids, while the diffusion approximation has been adopted for the radiation transport. The conclusions deduced are in agreement with the predictions of the theory of late stellar evolution.     

On a discription of dynamical properties of the gravitational field in vacuum

Die PETROV -Darstellung der Vakuum-Feldgleichungs-Klassifizierung wird diskutiert. Die Einführung kanonischer Tetraden führt zu einer Energiedefinition, die auf die Ricci-Rotationskoeffizienten basiert.