arXiv subjects
Publications and source records attributed to V. M. Lipunov.
We present here an updated description of the "Scenario Machine" code. This tool is used to carry out a population synthesis of binary stars. Previous version of the description can be found at http://xray.sai.msu.ru/~mystery//articles/review/contents.html
Using the ``Scenario Machine'' we have carried out a population synthesis of X-ray binaries for the purpose of modelling of X-ray luminosity functions (XLFs) in different types of galaxies: star burst, spiral, and elliptical. This computer code allows to calculate, by using Monte Carlo simulations, the evolution of a large ensemble of binary systems, with proper accounting for the spin evolution of magnetized neutron stars. We show that the XLF has no universal type. It depends on the star formation rate in the galaxy. Also it is of importance to take into account the evolution of binary systems and life times of X-ray stages in theoretical models of such functions. We have calculated cumulative and differential XLFs for the galaxy with the constant star formation rate. Also we have calculated cumulative luminosity functions for different intervals of time after the star formation burst in the galaxy and curves depicting the evolution of the X-ray luminosity after the star formation burst in the galaxy.
We analyze here late evolutionary stages of massive (with initial mass higher than 8 masses of the Sun) close binary stars. Our purposes are to study possible mechanisms of gamma ray bursts (GRBs) origin. We suppose in this paper that GRB phenomenon require formation of massive (approx. 1 M_sun) compact (approx. 10 km) accretion disks around Kerr black holes and neutron stars. Such Kerr black holes are products of collapse of Wolf-Rayet stars in extremely close binaries and merging of neutron stars with black holes and neutron stars with neutron stars in close binary systems. Required accretion disks also can be formed around neutron stars which were formed during collapse of accreting oxygen-neon white dwarfs. We have estimated frequencies of events which lead to a rotational collapse concerned with formation of rapidly rotating relativistic objects in the Galaxy. We made our calculations using the "Scenario Machine".
Using "Scenario Machine" we have carried out population synthesis of radio pulsar with black hole binaries (BH+Psr) in context of the most wide assumptions about star mass loss during evolution, binary stars mass ratio distribution, kick velocity and envelope mass lost during collapse. Our purpose is to display that under any suppositional parameters of evolution scenario BH+Psr population have to be abundant in Galaxy. It is shown that in the all models including models evolved by Heger et al. (2002), Woosley et al. (2002), Heger et al. (2003) expected number of the black holes paired with radio pulsars is sufficient enough to discover such systems within the next few years.
We present the first russian robot-telescope designed to make prompt observations of gamma-ray bursts (http://observ.pereplet.ru). The telescopes are near Moscow. The system of telescopes with prompt pointing rates connects to the internet. The main parameters are the following: Richter-Slefogt system telescope (355 mm, f/d=2.4); Richter-Slefogt system telescope (200mm, f/d=2.4); Flugge system telescope (280mm, f/d=2.5); TV-camera with 20x40 degree objective; Two CCD cameras (Pictor 416); One CCD Apogee Camera AP16E. The type of mount is German with 8 grad/sec slew rate. MASTER images stars down to 19 magnitude in a 1 min exposure covering 6 square degrees.
Recent discovery of the rate of expansion of the Universe (Reiss A.G. et al., 1998; Perlimutter S. et al., 1999) is connected with the vacuum energy in space which, in turn, can be considered (Gliner E.B., 1965) as the cosmological constant in Einstein's equation. In this article the cosmological term predicted by Einstein is interpreted in terms of World's mass required by Mach's principle. The Mach's principle itself is formulated as follows: inertia masses of bodies, including those of fundamental particles, are determined by the value of the cosmological term.
In this paper we present calculations of period distribution for old accreting isolated neutron stars (INSs). At the age about a few billions years low velocity INSs come to the stage of accretion. At that stage their period evolution is governed by magnetic breaking and accreted angular momentum. Due to turbulence of the interstellar medium (ISM) accreted momentum can both accelerate and decelerate rotation of an INS and spin evolution has chaotic character. Calculations show that for constant magnetic fields INSs have relatively long spin periods, $\ge 10^4$--$10^5$ s, depending on parameters of INSs and an ISM. Due to long periods INSs have high spin up/spin down rates, which should fluctuate on a time scale about a few years.
The first generation of long-baseline laser interferometric detectors of gravitational waves will start collecting data in 2001-2003. We carefully analyse their planned performance and compare it with the expected strengths of astrophysical sources. The scientific importance of the anticipated discovery of various gravitatinal wave signals and the reliability of theoretical predictions are taken into account in our analysis. We try to be conservative both in evaluating the theoretical uncertainties about a source and the prospects of its detection. After having considered many possible sources, we place our emphasis on (1) inspiraling binaries consisting of stellar mass black holes and (2) relic gravitational waves. We draw the conclusion that inspiraling binary black holes are likely to be detected first by the initial ground-based interferometers. We estimate that the initial interferometers will see 2-3 events per year from black hole binaries with component masses 10-15M_\odot, with a signal-to-noise ratio of around 2-3, in each of a network of detectors consisting of GEO, VIRGO and the two LIGOs. It appears that other possible sources, including coalescing neutron stars, are unlikely to be detected by the initial instruments. We also argue that relic gravitational waves may be discovered by the space-based interferometers in the frequency interval 2x10^{-3}-10^{-2} Hz, at the signal-to-noise ratio level around 3.
In this article we briefly review our recent results on evolution and properties of isolated neutron stars (INSs) in the Galaxy. As the first step we calculate a {\it census} of INSs in our Galaxy. We infer a lower bound for the mean kick velocity of NSs, $ \sim $(200-300) ${\rm km s^{-1}}$. The same conclusion is reached for both a constant magnetic field ($B\sim 10^{12}$ G) and for a magnetic field decaying exponentially with a timescale $\sim 10^9$ yr. These results, moreover, constrain the fraction of low velocity stars, which could have escaped pulsar statistics, to $\sim$few percents. Then we show that the range of minimum value of magnetic moment, $μ_b$: $\sim 10^{29.5}\ge μ_b \ge 10^{28} {\rm G} {\rm cm}^3$, and the characteristic decay time, $t_d$: $\sim 10^8\ge t_d \ge 10^7 {\rm yrs}$, can be excluded assuming the standard initial magnetic momentum, $μ_0=10^{30} {\rm G} {\rm cm}^3$, if accreting INSs are observed. For these parameters an INS would never reach the stage of accretion from the interstellar medium even for a low space velocity of the star and high density of the ambient plasma. The range of excluded parameters increases for lower values of $μ_0$. It is shown that old accreting INSs become more abundant than young cooling INSs at X-ray fluxes below $\sim 10^{-13}$ erg cm$^{-2}$ s$^{-1}$. We can predict that about one accreting INS per square degree should be observed at the {\it Chandra} and {\it Newton} flux limits of $\sim 10^{-16}$ erg cm$^{-2}$ s$^{-1}.$ The weak {\it ROSAT} sources, associated with INSs, can be young cooling objects, if the NSs birth rate in the solar vicinity during the last $\sim 10^6$ yr was much higher than inferred from radiopulsar observations.
The stages that follow the merging of two neutron stars are discussed. It is shown that if a rapidly rotating gravitationally bound object is formed after the merging (a spinar or a massive neutron star), then the characteristic time of its evolution is determined by a fundamental value t_{spin} = 3 k (m_p e^2 \hbar^{1/2}) / (m_e^3 c^{5/2} G^{1/2}) \approx 7e+5 s k, where the dimensionless value k depends on the exact equation of state of nuclear matter. The hypothesis is discussed as to whether the residual optical emission of the gamma-ray burst GRB 970228 is pulsar-like and its evolution driven by magnetodipole energy losses. It is shown that binary neutron star mergings can be accompanied by two gravitational wave burst separated either by the time interval t_{spin} or neutron star cooling time (~10 s), depending on the masses of neutron stars.
This paper is a continuation and development of our previous articles (Popov et al., 1997, 1998). We use `Scenario Machine'' (Lipunov et al., 1996b) -- the population synthesis simulator (for single binary systems calculations the program is available in WWW: http://xray.sai.msu.ru/ (Nazin et al., 1998)) -- to calculate evolution of populations of several types of X-ray sources during the first 20 Myrs after a starformation burst. We examined the evolution of 12 types of X-ray sources in close binary systems (both with neutron stars and with black holes) for different parameters of the IMF -- slopes: $α=1$, $α=1.35$ and $α=2.35$ and upper mass limits, $M_{up}$: 120 $M_{\odot}$, 60 $M_{\odot}$ and 40 $M_{\odot}$. Results, especially for sources with black holes, are very sensitive to variations of the IMF, and it should be taken into account when fitting parameters of starformation bursts. Results are applied to several regions of recent starformation in different galaxies: Tol 89, NGC 5253, NGC 3125, He 2-10, NGC 3049. Using known ages and total masses of starformation bursts (Shaerer at al., 1998) we calculate expected numbers of X-ray sources in close binaries for different parameters of the IMF. Usually, X-ray transient sources consisting of a neutron star and a main sequence star are most abundant, but for very small ages of bursts (less than $\approx 4$ Myrs) sources with black holes can become more abundant.
Estimates of the magnetic field of neutron stars in X-ray pulsars are obtained using the hypothesis of the equilibrium period for disk and wind accretion and also from the BATSE data on timing of X-ray pulsars using the observed maximum spin-down rate. Cyclotron lines at energies $\ge 100$ keV in several Be-transient are predicted for future observations. We suggest a new method of estimating distances to X-ray pulsars and their magnetic fields. Using observations of fluxes and period variations in the model of disk accretion one can estimate the magnetic momentum of a neutron star and the distance to X-ray pulsar. As an illustration the method is applied to the system GROJ1008-57.
The paucity of old isolated accreting neutron stars in ROSAT observations is used to derive a lower limit on the mean velocity of neutron stars at birth. The secular evolution of the population is simulated following the paths of a statistical sample of stars for different values of the initial kick velocity, drawn from an isotropic Gaussian distribution with mean velocity $0\leq < V>\leq 550$ ${\rm km s^{-1}}$. The spin-down, induced by dipole losses and the interaction with the ambient medium, is tracked together with the dynamical evolution in the Galactic potential, allowing for the determination of the fraction of stars which are, at present, in each of the four possible stages: Ejector, Propeller, Accretor, and Georotator. Taking from the ROSAT All Sky Survey an upper limit of $\sim 10$ accreting neutron stars within $\sim 140$ pc from the Sun, we infer a lower bound for the mean kick velocity, $ < V>\ga 200-300$ ${\rm km s^{-1}}$. The same conclusion is reached for both a constant ($B\sim 10^{12}$ G) and a magnetic field decaying exponentially with a timescale $\sim 10^9$ yr. Present results, moreover, constrain the fraction of low velocity stars, which could have escaped pulsar statistics, to $\la 1%$.
The paucity of old isolated accreting neutron stars in ROSAT observations is used to derive a lower limit on the mean velocity of neutron stars at birth. The secular evolution of the population is simulated following the paths of a statistical sample of stars for different values of the initial kick velocity, drawn from an isotropic Gaussian distribution with mean velocity $0\leq < V>\leq 550$ ${\rm km s^{-1}}$. The spin--down, induced by dipole losses and the interaction with the ambient medium, is tracked together with the dynamical evolution in the Galactic potential, allowing for the determination of the fraction of stars which are, at present, in each of the four possible stages: Ejector, Propeller, Accretor, and Georotator. Taking from the ROSAT All Sky Survey an upper limit of $\sim 10$ accreting neutron stars within $\sim 140$ pc from the Sun, we infer a lower bound for the mean kick velocity, $ < V>\gtrsim 200-300$ ${\rm km s^{-1}},$ corresponding to a velocity dispersion $σ_V\gtrsim 125-190$ km s$^{-1}$. The same conclusion is reached for both a constant magnetic field ($B\sim 10^{12}$ G) and a magnetic field decaying exponentially with a timescale $\sim 10^9$ yr. Such high velocities are consistent with those derived from radio pulsar observations. Present results, moreover, constrain the fraction of low velocity stars, which could have escaped pulsar statistics, to less than 1%.
Estimates of the magnetic field of neutron stars in X-ray pulsars are obtained using the hypothesis of the equilibrium period for disk and wind accretion and also from the BATSE data on timing of X-ray pulsars using the observed maximum spin-down rate. Cyclotron lines at energies $\ge 100$ keV in several Be-transient are predicted for future observations.
We show that the distribution of observed energies of GRB with known redshifts can be explained by the hypothesis of the standard energy release E_0=5 10^51 ergs. Two situations are possible, either the beaming angle differs from burst to burst, or there is a universal emssion diagram in each burst, the observed difference being due to different viewing angles.
This paper is a continuation and development of our previous articles (Popov et al., 1997, 1998). We use ``Scenario Machine'' (Lipunov et al., 1996b) -- the population synthesis simulator (for single binary systems calculations the program is available in WWW at: http://xray.sai.msu.su/sciwork/scenario.html (Nazin et al., 1998) -- to calculate evolution of populations of several types of X-ray sources during the first 20 Myrs after a starformation burst. We examined the evolution of 12 types of X-ray sources in close binary systems (both with neutron stars and with black holes) for different parameters of the IMF -- slopes: $α=1, α=1.35$ and $α=2.35$ and upper mass limits: 120 M_{\odot}, 60 M_{\odot} and 40 M_{\odot}. Results, especially for sources with black holes, are very sensitive to variations of the IMF, and it should be taken into account when fitting parameters of starformation bursts. Results are applied to several regions of recent starformation in different galaxies: Tol 89, NGC 5253, NGC 3125, He 2-10, NGC 3049. Using known ages and total masses of starformation bursts (Shaerer at al., 1998) we calculate expected numbers of X-ray sources in close binaries for different parameters of the IMF. Usially, X-ray transient sources consisting of a neutron star and a main sequence star are most abundant, but for very small ages of bursts (less than $\approx 4$ Myrs) sources with black holes can become more abundant.
In this article we use "Scenario Machine" - the population synthesis simulator- to calculate the evolution of the populations of the selected types of X-ray sources after the starformation burst with the total mass in binaries $1.5\cdot10^6 M_{\odot}$ during the first 20 Myr after the burst. Sources of the four types were calculated: transient sources- accreting neutron stars with Be- stars; accreting neutron stars in pair with supergiants; Cyg X-1-like sources- black holes with supergiants; superaccreting black holes. We used two values of the $α- coefficient$ in the mass-function: 2.35 (Salpeter's function) and 1.01 ("flat spectrum"). The calculations were made for two values of the upper limit of the mass-function: 120 and 30 $M_{\odot}$. For the flat spectrum the number of sources of all types significantly increased. Decreasing of the upper mass limit below the critical mass of a black hole formation increase (for the "flat spectrum") the number of transient sources with neutron stars up to $\approx 300$. We give approximating formulae for the time dependence of source numbers.