Motion of the components of a close binary system in a strong external gravitational field

The motion of the components of a close binary system near a very massive body is investigated within the framework of the three-body problem. Cases requiring consideration of relativistic effects are also examined. It is shown that the close binary system often breaks up at some distance from the very massive body on approaching it. In many cases, the breakup of the close binary system is preceded by an abrupt decrease in the separation of its components. Possible consequences of close binary system breakup for the abundance of such systems in galaxies are discussed briefly.Translated fromAstrofizika, Vol. 39, No. 2, pp. 243–250, April–June, 1996.     

The cross-correlation between galaxies and groups: probing the galaxy distribution in and around dark matter haloes

Some massive binaries should contain energetic pulsars which inject relativistic leptons from their inner magnetospheres and/or pulsar wind regions. If the binary system is compact enough, then these leptons can initiate inverse Compton (IC) e^± pair cascades in the anisotropic radiation field of a massive star. γ-rays can be produced in the IC cascade during its development in a pulsar wind region and above a shock in a massive star wind region where the propagation of leptons is determined by the structure of a magnetic field around the massive star. For a binary system with specific parameters, we calculate phase-dependent spectra and fluxes of γ-rays escaping as a function of the inclination angle of the system and for different assumptions on injection conditions of the primary leptons (their initial spectra and location of the shock inside the binary). We conclude that the features of γ-ray emission from such massive binaries containing energetic pulsars should allow us to obtain important information on the acceleration of particles by the pulsars, and on interactions of a compact object with the massive star wind. Predicted γ-ray light curves and spectra in the GeV and TeV energy ranges from such binary systems within our Galaxy and Magellanic Clouds should be observed by future AGILE and GLAST satellites and low-threshold Cherenkov telescopes, such as MAGIC, HESS, VERITAS or CANGAROO III.     

The influence of the radiation pressure force on possible critical surfaces in binary systems

Using a spherically symmetric approximation for the radiation pressure force to compute a possible critical surface for binary systems, previous authors found that the surface opens up at the far side of the companion. It is shown that this effect may be unreal, and could be a consequence of the simple approximation for the radiation pressure force. Due to the influence of the radiation force, mass will be lost over the whole surface of the star. In that way much mass could leave the system in massive binary systems. On the basis of evolutionary models, including mass loss by stellar wind, our results were applied on the X-ray binaries 3U 1700-37 and HD 77581.     

Mass transfer and loss of the massive semi-detached binary AI Crucis

AI Crucis is a short-period semi-detached massive close binary (P = 1.41771d, Sp.=B1.5) in the open cluster NGC 4103. It is a good astrophysical laboratory for investigating the formation and evolution of massive close binary stars via case A mass transfer. Orbital period variations of the system were analyzed based on one newly determined eclipse time and the others compiled from the literature. It is discovered that the orbital period of the binary is continuously increasing at a rate of dP/dt = +1.00(±0....     

Simulation and analysis of the dynamics of binary near-Earth Asteroid (66391) 1999 KW4

Near-Earth Asteroid (66391) 1999 KW4 was the subject of the recently published first extensive radar imaging, shape and mutual orbit modeling, and physical and dynamical characterization of a binary asteroid. In this paper we present in detail our numerical simulation of KW4 behind that work. Our propagations of the system with some variation in estimated parameters cover the set of KW4's possible current dynamical states consistent with the body models and other information obtained directly from the observations. We also apply our implementation of this simulation capability to address some of the dynamical mechanisms by which KW4 may be moved into the more energetically excited of those possible current states, particularly solar gravity interaction. Through comparison of the results with certain features of the observation data, we conclude that the actual KW4 system is not in the most energetically relaxed configuration but must be moderately excited. The system occupies a generalized Cassini state 2 which is different from that considered in most previously published treatments of Cassini states in that it involves co-precession of the primary's spin frame and the mutual orbit rather than co-precession of a satellite's spin frame and that satellite's orbit about the primary. We present a simple analytical theory describing the system's dynamics, which should be applicable to any other binary systems, of which KW4 is representative, in which a massive, roughly oblate primary is spinning rapidly relative to the rate of its mutual orbit with an on-average synchronous, elongated secondary. We examine separately both the effect of the larger binary component's oblateness, and the effect of the smaller component's roughly triaxial ellipsoid shape. The simple analytical formulae obtained agree with full-detail numerical simulation results, and can be used for remote estimation of binary mass properties from observed system motion.     

Hyperfast pulsars as the remnants of massive stars ejected from young star clusters

Recent proper motion and parallax measurements for the pulsar PSR B1508+55 indicate a transverse velocity of  ∼1100 km s⁻¹  , which exceeds earlier measurements for any neutron star. The spin-down characteristics of PSR B1508+55 are typical for a non-recycled pulsar, which implies that the velocity of the pulsar cannot have originated from the second supernova disruption of a massive binary system. The high velocity of PSR B1508+55 can be accounted for by assuming that it received a kick at birth or that the neutron star was accelerated after its formation in the supernova explosion. We propose an explanation for the origin of hyperfast neutron stars based on the hypothesis that they could be the remnants of a symmetric supernova explosion of a high-velocity massive star which attained its peculiar velocity (similar to that of the pulsar) in the course of a strong dynamical three- or four-body encounter in the core of dense young star cluster. To check this hypothesis, we investigated three dynamical processes involving close encounters between: (i) two hard massive binaries, (ii) a hard binary and an intermediate-mass black hole (IMBH) and (iii) a single stars and a hard binary IMBH. We find that main-sequence O-type stars cannot be ejected from young massive star clusters with peculiar velocities high enough to explain the origin of hyperfast neutron stars, but lower mass main-sequence stars or the stripped helium cores of massive stars could be accelerated to hypervelocities. Our explanation for the origin of hyperfast pulsars requires a very dense stellar environment of the order of  10⁶– 10⁷ stars pc⁻³  . Although such high densities may exist during the core collapse of young massive star clusters, we caution that they have never been observed.     

Model for the explosion of a critical-mass neutron star in a binary system

A series of numerical models has been constructed for the three-dimensional explosion dynamics of a low-mass neutron star in a binary system that results from the collapse of the rotating iron core of a massive supernova. The numerical solution has been obtained by the particle method with an adaptive time step that allows the computational accuracy to be controlled automatically. The constructed numerical models include the proper motion of the massive component in the binary system of neutron stars, their finite sizes, the graduality of energy release during the explosive disruption of a critical-mass neutron star, and the nonuniform expansion velocity distribution of iron ejecta. The extent to which each of the listed parameters affects the explosion characteristics has been determined. The total explosion energy and the pulsar escape velocity have been estimated. A sizable fraction of the material of the exploded neutron star has been found to remain gravitationally bound to the massive component of the binary system. A further study of its dynamics is of interest in its own right, because the captured material can be considered as an additional source of muon neutrinos.     

Extragalactic binaries as core-collapse supernova progenitors

Binary star systems are likely the progenitors of many core-collapse (Type II, Type Ib/c) supernovae (SNe). We present observational investigations using ground-based and Hubble Space Telescope optical imaging and radio monitoring of SNe and their environments, which either indicate or attempt to constrain the possible binary nature of the SN progenitors. For example, from radio observations with the Very Large Array of the Type II-linear SN 1979C in M100 we conclude that the progenitor was possibly in a massive, highly eccentric binary, similar to the VV Cephei systems. The Type IIb SN 1993J in M81 is presumed to have a massive progenitor in an interacting binary system, and from Hubble imaging we cannot yet constrain the nature of the presumed massive, blue companion. We will present additional results for other Type Ib/c and II SNe.     

The Orbit Computation of Binary Black Hole OJ287—A 3.5-th Order Post-Newtonian Approximation

The massive binary black hole OJ287 is a source of intense gravita- tional radiation. To detect the signal of its gravitational waves, a knowledge of the signal waveform will be of great help, and this is mainly determined by the orbital motion of the binary. For this, we carry out a detailed calculation on the orbital motion of OJ287, using the post-Newtonian (PN) approximation up to the 3.5th order within the framework of general relativity. Our result is one order higher than the previous work made by others. As in the process of radiation, there is a time delay from the instance when the secondary black hole impacts on the accretion disk of the primary to the moment of the optical outburst. This time delay has to be taken into consideration when we try to fit the calculating orbit with the observed times of outbursts. Adopting a linear relation between the time delay and the impact distance as an empirical model, we fit the cal- culating orbit with the recent 7 outbursts of OJ287, and obtain the solution of its orbital motion, as well as its averaged orbital parameters. By analyzing the result of 3.5 PN order calculation of the binary system, we find some interesting features. In the early period, the rate of precession of the secondary black hole increases, while in the late period approximate to merging, the rate of precession attains its maximum. Afterwards it diminishes, and finally becomes negative. At present we cannot determine whether this behavior is due to the insuffcient accuracy of the 3.5-th order approximation. For the term of dissipative radiation in the equation of motion, the coeffcients of the 2.5 and 3.5 PN orders possess opposite signs. This implies that the 3.5-th order term represents the absorption of energy from outside. However, the sum of the 2.5-th order and 3.5-th order terms still behaves as radiating gravitational waves outward, the rate of energy variation of the system is negative. The calculated result of this work may be useful for more accurate calculations of the gravitational radiation of OJ287.     

The impact of a supernova explosion in a very massive binary

We consider the effect of a supernova (SN) explosion in a very massive binary that is expected to form in a portion of Population III stars with the mass higher than  100 M_⊙  . In a Population III binary system, a more massive star can result in the formation of a black hole (BH) and a surrounding accretion disc. Such BH accretion could be a significant source of the cosmic reionization in the early Universe. However, a less massive companion star evolves belatedly and eventually undergoes a SN explosion, so that the accretion disc around a BH might be blown off in a lifetime of companion star. In this paper, we explore the dynamical impact of a SN explosion on an accretion disc around a massive BH, and elucidate whether the BH accretion disc is totally demolished or not. For the purpose, we perform three-dimensional hydrodynamic simulations of a very massive binary system, where we assume a BH of  10³ M_⊙  that results from a direct collapse of a very massive star and a companion star of  100 M_⊙  that undergoes a SN explosion. We calculate the remaining mass of a BH accretion disc as a function of time. As a result, it is found that a significant portion of gas disc can survive through three-dimensional geometrical effects even after the SN explosion of a companion star. Even if the SN explosion energy is higher by two orders of magnitude than the binding energy of gas disc, about a half of disc can be left over. The results imply that the Population III BH accretion disc can be a long-lived luminous source, and therefore could be an important ionizing source in the early Universe.     

大质量双星系统的非守恒演化

由于大质量双星系统有强大的星风物质损失,因而在研究其结构和演化时必须考虑星风物质损失,动量损失,物质交换以及由以上原因引起的轨道参量的变化,此外,天文观测又证实,一些大质量双星系统中存在星风冲击波,有Ｘ射线辐射以及有致密天体（白矮星,中子星）的存在,因此在研究大质量双星的演化时,又会遇到在星风冲击波理论及其对演化的影响,双星系统何时会演化成为公共外壳的系统,以及双星系统中如果发生超新星爆发,是否会     

On the binarity of Herbig Ae/Be stars

We present high-resolution spectro-astrometry of a sample of 28 Herbig Ae/Be and three F-type pre-main-sequence stars. The spectro-astrometry, which is essentially the study of unresolved features in long-slit spectra, is shown from both empirical and simulated data to be capable of detecting binary companions that are fainter by up to 6 mag at separations larger than ∼0.1 arcsec. The nine targets that were previously known to be binary are all detected. In addition, we report the discovery of six new binaries and present five further possible binaries. The resulting binary fraction is 68 ± 11 per cent. This overall binary fraction is the largest reported for any observed sample of Herbig Ae/Be stars, presumably because of the exquisite sensitivity of spectro-astrometry for detecting binary systems. The data hint that the binary frequency of the Herbig Be stars is larger than that of the Herbig Ae stars. The Appendix presents model simulations to assess the capabilities of spectro-astrometry and reinforces the empirical findings. Most spectro-astrometric signatures in this sample of Herbig Ae/Be stars can be explained by the presence of a binary system. Two objects, HD 87643 and Z CMa, display evidence for asymmetric outflows. Finally, the position angles of the binary systems have been compared with available orientations of the circumprimary disc and these appear to be coplanar. The alignment between the circumprimary discs and the binary systems strongly suggests that the formation of binaries with intermediate-mass primaries is due to fragmentation as the alternative, stellar capture, does not naturally predict aligned discs. The alignment extends to the most massive B-type stars in our sample. This leads us to conclude that formation mechanisms that do result in massive stars, but predict random angles between the binaries and the circumprimary discs, such as stellar collisions, are also ruled out for the same reason.     

Accretion disc in the massive V448 Cygni system

The UBV light curves of the early-type eclipsing binary V448 Cygni, obtained at the Abastumani Astrophysical Observatory from 1964 to 1967, are re-analysed here. The analysis was made assuming the presence of an accretion disc in the system, as inferred from the light-curve shape and spectroscopic characteristics of the system. The Roche model of a binary was used, containing a geometrically and optically thick accretion disc around the hotter and more massive star. By solving the inverse problem, the orbital elements and the physical parameters of the system components and of the accretion disc were estimated. This result is important for understanding the star formation and evolution processes in the systems with massive components.     

Gravitational wave radiation from the coalescence of white dwarfs

We compute the emission of gravitational radiation from the merging of a close white dwarf binary system. This is done for a wide range of masses and compositions of the white dwarfs, ranging from mergers involving two He white dwarfs, through mergers in which two CO white dwarfs coalesce, to mergers in which a massive ONe white dwarf is involved. In doing so we follow the evolution of the binary system using a smoothed particle hydrodynamics code. Even though the coalescence process of the white dwarfs involves considerable masses, moving at relatively high velocities with a high degree of asymmetry we find that the signature of the merger is not very strong. In fact, the most prominent feature of the coalescence is that in a relatively small time-scale (of the order of the period of the last stable orbit, typically a few minutes) the sources stop emitting gravitational waves. We also discuss the possible implications of our calculations for the detection of the coalescence within the framework of future space-borne interferometers like LISA.     

Long–term Photometry of RT Lacertae: 2. Further Evidence fo a Circumstellar Envelope and MAss Accretion

The light curves, obtained by the authors of the present paper during the period 1978–1992, of the chromospherically active binary system RT Lac were examined. The average (B–V) colour indices were obtained and corrected for the interstellar extinction. Spectroscopic studies indicate that the less massive component may be taken as G8. The light curve analysis indicates that the less massive, larger component fills its corresponding Roche lobe. Both photometric and spectroscopic observations compel one to draw a conclusion that circumstellar matter does exist around the binary system. A colour excess caused by this matter is found to be 0.278 for B–V colour at mid–secondary eclipse. On the basis of photometric colour indices alone, the components of RT Lac are classified as G3–4 and G8. If we use the observed radial velocities of the less massive subgiant star from Ca II emission lines and from other optical lines we find for the mass of the more massive component as 1.34–1.70 M. This mass range corresponds to the main sequence late F stars. The common envelope hypothesis and mass function and also blending of the spectral lines of more massive component point out that it should be at most a late F type main sequence star.     

Photoelectric photometry of eclipsing binary V375 cassiopeiae

Some 604 photoelectric BV observations of the eclipsing binary V375 Cas were obtained at Beijing Observatory from August to November 1982. Photometric solution was carried out using the Wilson-Devinney program for the BV light curves. The system is found to be a semidetached binary in which the less massive component fills its Roche lobe and the more massive component nearly does so. It is very similar to RZ Dra. This very interesting system is important for the understanding of the evolution of close binaries.     

The relative motion of two spheroidal rigid bodies

We consider two spheroidal rigid bodies of comparable size constituting the components of an isolated binary system. We assume that (1) the bodies are homogeneous oblate ellipsoids of revolution, and (2) the meridional eccentricities of both components are small parameters.We obtain seven nonlinear differential equations governing simultaneously the relative motion of the two centroids and the rotational motion of each set of body axes. We seek solutions to these equations in the form of infinite series in the two meridional eccentricities.In the zero-order approximation (i. e., when the meridional eccentricities are neglected), the equations of motion separate into two independent subsystems. In this instance, the relative motion of the centroids is taken as a Kepler elliptic orbit of small eccentricity, whereas for each set of body axes we choose a composite motion consisting of a regular precession about an inertial axis and a uniform rotation about a body axis.The first part of the paper deals with the representation of the total potential energy of the binary system as an infinite series of the meridional eccentricities. For this purpose, we had to (1) derive a formula for representing the directional derivative of a solid harmonic as a combination of lower order harmonics, and (2) obtain the general term of a biaxial harmonic as a polynomial in the angular variables.In the second part, we expound a recurrent procedure whereby the approximations of various orders can be determined in terms of lower-order approximations. The rotational motion gives rise to linear differential equations with constant coefficients. In dealing with the translational motion, differential equations of the Hill type are encountered and are solved by means of power series in the orbital eccentricity. We give explicit solutions for the first-order approximation alone and identify critical values of the parameters which cause the motion to become unstable.The generality of the approach is tantamount to studying the evolution and asymptotic stability of the motion.Research performed under NASA Contract NAS5-11123.     

Binaries in the universe. possible dynamical mechanisms of formation,evolution and disruption of different kinds of constituents of the universe

We study the dynamics of extended shells of relatively low-mass particles around and inside the orbit of two heavy centres of gravity (a binary) by computer simulations. The binary components are surrounded byN = 16 000 small mass particles in uniform random distribution on few spherical envelopes with different radii expanding with respective velocities. Some shells are inside the orbit of binary.We apply this model to binary galaxy systems with baryonic dark matter, e.g., massive black holes. In principle, we can apply this model to different kinds of objects (from binary star systems until superclusters of galaxies).It is shown that the shell expands homologously with a decreasing velocity and then, falls back into the binary system forming zones of compressed matter. At some moment of time there could be a collapse of these particles on to the heavier component of the binary. Further in time, some part of particles which were outside the binary orbit escape from the system. Other particles which were initially inside of the orbit are captured by binary components.We consider a number of different models with different initial parameters. For models with smaller radii of shells, about one-half of the particles escape from systems; whereas for larger values the shell disrupts as a whole. Escaping particles form collimated flows in planes of orbits of binaries. Positions of flows and directions of motion depend on positions of heavier components of binaries at the moment of a closest approach of particles and on ratios of masses of binary components.We show that during evolution of our models different kinds of structures of systems often are very similar to the observed structures of galaxies: spiral and elliptical galaxies, interacting galaxies, different kinds of flows and jets. Totally systems are expanding - after 40 periods of rotation of the binary the system expands by 300 times.     

Equilibrium points and Lyapunov families in the circular restricted three-body problem with an oblate primary and a synchronous rotating dipole secondary: Application to Luhman-16 binary system

We numerically study a version of the synchronous circular restricted three-body problem, where an infinitesimal mass body is moving under the Newtonian gravitational forces of two massive bodies. The primary body is an oblate spheroid while the secondary is an elongated asteroid of a combination of two equal masses forming a rotating dipole which is synchronous to the rotation of the primaries of the classic circular restricted three-body problem. In this paper, we systematically examine the existence, positions, and linear stability of the equilibrium points for various combinations of the model's parameters. We observe that the perturbing forces have significant effects on the positions and stability of the equilibrium points as well as the regions where the motion of the particle is allowed. The allowed regions of motion as determined by the zero-velocity surface and the corresponding isoenergetic curves as well as the positions of the equilibrium points are given. Finally, we numerically study the binary system Luhman-16 by computing the positions of the equilibria and their stability as well as the allowed regions of motion of the particle. The corresponding families of periodic orbits emanating from the collinear equilibrium points are computed along with their stability properties.     

The mass ratio distribution of MBH binaries in the hierarchical model

We present different mass ratio distributions of massive black hole(MBH)binaries due to different mechanisms involved in binary evolution. A binary system of MBHs forms after the merger of two galaxies, which has three stages: the dynamical friction stage, the stellar scattering or circumbinary disk stage, and the gravitational radiation stage. The second stage was once believed to be the "final parsec problem"(FPP) as the binary stalled at this stage because of the depletion of stars. Now, the FPP has been shown to no longer be a problem. Here we get two different mass ratio distributions of MBH binaries under two mechanisms, stellar scattering and the circumbinary disk interaction. For the circumbinary disk mechanism, we assume that the binary shrinks by interaction with a circumbinary disk and the two black holes(BHs)have different accretion rates in the simulation. We apply this simple assumption to the hierarchical coevolution model of MBHs and dark matter halos, and we find that there will be more equal-mass MBH binaries in the final coalescence for the case where the circumbinary mechanism operates. This is mainly because the secondary BH in the circumbinary disk system accretes at a higher rate than the primary one.