arXiv subjects

K. A. Postnov

Publications and source records attributed to K. A. Postnov.

118 records · Page 7Linked to original sources

arXiv1997

Merging Rates of Compact Binaries in the Universe: Gravitational Waves and Gamma-Ray Bursts

Merging rates of compact binaries (double neutron stars or black holes) are calculated based on the modern concept of binary stellar evolution. It is found that the initial laser interferometers with an rms-sensitivity of $10^{-21}$ at the frequency 100 Hz can detect 10-700 black holes and only \sim 1 neutron star coalescences in a 1-year integration time. Implications of the evolutionary effects to the cosmological origin of GRB are also discussed.

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arXiv1997

Formation and coalescence of relativistic binary stars: effect of kick velocity

Galactic binary pulsars with different companion types (OB-star, white dwarf (WD), neutron star (NS), black hole (BH), or planet) assuming various phenomenological distributions for kick velocities of newborn NS are studied. The merging rates of relativistic binary stars (NS+NS, NS+BH, BH+BH) dependence on the kick velocity is specially adresed. The BH+BH merging is shown to occur, depending on parameters of BH formation, at a rate of one per 200,000 -- 500,000 years in a Milky Way type galaxy. The NS+NS merging rate $R_{ns}$ is found to be 1 per \sim 3,000 years for zero recoil, and decrease to one per 10,000 years even for the highest kick velocities of 400 km/s. That the merging rates derived from evolutionary calculations are by two order of magnitude higher than those based on binary pulsar statistics only, is suggested to be due to the fact that the observable binary pulsars in pairs with NS form only a fraction of the total number of binary NS systems. The expected detection rate of binary BH by a LIGO-type gravitational wave detector comparable with and even higher than the binary NS merging rate for a wide range of parameters.

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arXiv1997

Black holes and gravitational waves: simultaneous discovery by initial laser interferometers

Study of gravitational-radiation induced merging rates of relativistic binary stars (double neutron stars; neutron star + black hole; double black holes) shows that the first-generation gravitational wave interferometers with an rms-sensitivity of $10^{-21}$ at frequency 100 Hz can detect 10-700 black hole and only $\sim 1$ neutron star coalescences in a 1-year integration time in a wide range of stellar evolution parameters. It is notable that modern concepts of stellar evolution predict that the first detection of gravitational wave will independently discover black holes.

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arXiv1997

High Neutron Star Birth Velocities and Gravitational Radiation during Supernova Explosions

Assuming the observed pulsar velocities to originate during asymmetric collapse of stellar cores, we compute the amplitude of gravitational waves emitted during type II and Ib supernova explosions and their detection rate from within a distance of 30 Mpc. At the rms-level of advanced laser interferometers h ~ 1.0e-22 at frequencies 300-1000 Hz the expected rate is about 1 per year.

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arXiv1996

First LIGO events: binary black holes mergings

Based on evolutionary scenarios for binary stellar evolution we study the merging rates of relativistic binary stars (NS+NS, NS+BH, BH+BH) under different assumptions of BH formation. We find the BH+BH merging rate in the range one per 200,000 -- 500,000 year in a Milky-Way type galaxy, while the NS+NS merging rate $R_{ns}$ is approximately 10 times as high, which means that the expected event rate even for high mean kick velocities of NS up to 400 km/s is at least 30-50 binary NS mergings per year from within a distance of 200 Mpc. As typical BH is formed with a mass 3-10 times the NS mass (assumed 1.4 M$_\odot$), the rates obtained imply that the expected detection rate of binary BH by a LIGO-type gravitational wave detector is 10-100 times higher than the binary NS merging rate for a wide range of parameters.

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arXiv1996

Binary Evolution in World Wide Web

We present a WWW-version of the {\it Scenario Machine} - a computer code designed to calculate the evolution of close binary stellar systems. The Internet users can directly access to the code and calculate binary evolutionary tracks with parameters at the user's will. The program is running on the {\it Pentium} server of the Division of the Relativistic Astrophysics of the Sternberg Astronimical Institute (http://xray.sai.msu.su/ ). The results are presented both in the form of tables and graphic diagrams. The work is always in progress. More possibilities for Internet users are intended to become available in the near future.

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arXiv1995

Population synthesis of X-ray sources at the Galactic center

We model the evolution of the selected types of X-ray sources (both with BHs and NSs) for the star formation burst at the Galactic center. For the currently assumed starburst age of 4-7 millions years, our results are consistent with the recent {\it GRANAT} X-ray observations of the Galactic center and predict a substantial number of X-ray binaries with black holes. In addition we made a very simple model of the spatial distribution of the X-ray sources, which is also consistent with the {\it GRANAT} observations. The results can be applied to other starformation regions.

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arXiv1995

Population synthesis of X-ray sources at the Galactic center

X-ray binary population at the Galactic center is proposed here to form as a result of a starburst, which is synthesized by using the ``Scenario Machine'' code of binary star evolution. For the currently assumed starburst age of 4-7 millions years, our results are consistent with the recent {\it GRANAT} X-ray observations of the Galactic center and predict a substantial number of X-ray binaries with black holes.

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arXiv1995

Gravitational Radiation during Thorne-Zytkow object formation

Calculation of gravitational radiation during binary inspiral leading to possible formation of a Thorne-Zytkow (TZ) object (a neutron star inside a supergiant core) is performed. The calculations were done for polytropic density distributions with different indeces $n$, as well as for realistic models of supergiants. A maximum frequency of the emitted gravitational waves during this process was found to range from a few to 300 initial keplerian orbital frequensies, that is from $10^{-5}$ to $\sim 0.1$ Hz, depending on the model. A dimensionless strain metric amplitude can reach $h\sim 10^{-23.5}$ for a source lying 10 kpc away from the Sun. We conclude that TZ objects forming at a rate of 1 per 500 yrs in the Galaxy could be potential astrophysical targets for space laser intereferometers. Analysis of gravitational waveforms emitted during TZ-object formation could bring a unique information about stellar structure.

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arXiv1995

Evolution of the double neutron star merging rate and the cosmological origin of gamma-ray burst sources

Evolution of the coalescence rate of double neutron stars (NS) and neutron star -- black hole (BH) binaries are computed for model galaxies with different star formation rates. Assuming gamma-ray bursts (GRB) to originate from NS+NS or NS+BH merging in distant galaxies, theoretical logN--logS distributions and tests of gamma-ray bursts (GRB) are calculated for the first time taking the computed merging rates into account. We use a flat cosmological model (Omega=1) with different values of the cosmological constant Lambda and under various assumptions about the star formation history in galaxies. The calculated source evolution predicts a 5-10 times increase of the source statistics at count rates 3-10 times lower than the exising BATSE sensitivity limit. The most important parameter in fitting the 2nd BATSE catalogue is the initial redshift of star formation, which is found to be z_*=2-5 depending on a poorly determined average spectral index of GRB.

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