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1.
The current evolutionary stage of the binary systems IC 10 X-1 and NGC 300 X-1, which contain a massive black hole and a Wolf–Rayet star with a strong stellar wind that does not fill its Roche lobe, is considered. The high X-ray luminosity and X-ray properties testify to the presence of accretion disks in these systems. The consistency of the conditions for the existence of such a disk and the possibility of reproducing the observed X-ray luminosity in the framework of the Bondi–Hoyle–Littleton theory for a spherically symmetric stellar wind is analyzed. A brief review of information about the mass-loss rates of Wolf–Rayet stars and the speeds of their stellar winds is given. The evolution of these systems at the current stage is computed. Estimates made using the derived parameters show that it is not possible to achieve consistency, since the conditions for the existence of an accretion disk require that the speed of the Wolf–Rayetwind be appreciably lower than is required to reproduce the observedX-ray luminosity. Several explanations of this situation are possible: (1) the real pattern of the motion of the stellar-wind material in the binary is substantially more complex than is assumed in the Bondi–Hoyle–Littleton theory, changing the conditions for the formation of an accretion disk and influencing the accretion rate onto the black hole; (2) some of the accreting material leaves the accretor due to X-ray heating; (3) the accretion efficiency in these systems is nearly an order of magnitude lower than in the case of accretion through a thin disk onto a non-rotating black hole; (4) the intensity of the Wolf–Rayet wind is one to two orders of magnitude lower than has been suggested by modern studies. 相似文献
2.
We apply a population synthesis technique to study the formation and evolution of low-mass X-ray binaries with black holes, observed as X-ray novae, from hierarchical triple systems. A scenario is suggested in which an inner close binary system evolves into an X-ray system with a large mass ratio. The high rate of accretion onto the neutron star leads to a common envelope stage, which may result in the formation of a Thorne-Zytkow (TZ) object. During its evolution, the envelope of the TZ object expands, encompassing the third star. The recurrent common-envelope stage decreases the size of the orbit of the third star, leading to the formation of a lowmass X-ray nova with a black hole. The dynamical stability of triple systems automatically ensures that only lowmass X-ray novae form. We also consider the possible formation of an X-ray nova from a binary in the case of asymmetrical core collapse during a supernova explosion. 相似文献
3.
V. V. Nazarenko 《Astronomy Reports》2008,52(1):40-52
Three-dimensional numerical hydrodynamical modeling of a radiative wind and accretion disk in a close binary system with a compact object is carried out, using the massive X-ray binary LMC X-3 as an example. This system contains a precessing disk, and may have relativistic jets. These computations show that an accretion disk with a radius of about 0.20 (in units of the component separation) forms from the radiative wind from the donor when the action of the wind on the central source is taken into account, when the accretion rate is equal to the observed value (about 3.0 × 10?8 M ⊙/year, which corresponds to the case when the donor overflows its Roche lobe by nearly 1%). It is assumed that the speed of the donor wind at infinity is about 2200 km/s. The disk that forms is geometrically thick and nearly cylindrical in shape, with a low-density tunnel at its center extending from the accretor through the disk along the rotational axis. We have also modeled a flare in the disk due to short-term variations in the supply of material through the Lagrange point L1, whose brightnesses and durations are able to explain flares in cataclysmic variables and X-ray binaries. The accretion disk is not formed when the donor underfills its Roche lobe by 0.5%, which corresponds to an accretion rate onto the compact object of 2.0 × 10?9 M ⊙/year. In place of a disk, an accretion envelope with a radius of about 0.03 forms, within which gas moves along very steep spiral trajectories before falling onto the compact object. As in the accretion-disk case, a tunnel forms along the rotational axis of the accretion envelope; a shock forms behind the accretor, where flares occur in a compact region a small distance from the accretor at a rate of about six flares per orbital period, with amplitudes of about 10 m or more. The flare durations are two to four minutes, and the energies of individual particles at the flare maximum are about 100–150 keV. These flares appear to be analogous to the flares observed in gamma-ray and X-ray burst sources. We accordingly propose a model in which these phenomena are associated with massive, close X-ray binary systems with component-mass ratios exceeding unity, in which the donor does not fill its Roche lobe. Although no accretion disk forms around the compact object, an accretion region develops near the accretor, where the gamma-ray and X-ray flares occur. 相似文献
4.
We present the results of population syntheses obtained using our “scenario machine.” The mass spectra of black holes in X-ray binary systems before and after the stage of accretion from an optical companion are obtained for various evolutionary scenarios. The results of the model computations are compared to observational data. The observational data are used to estimate the fraction of a presupernova’s mass that collapses into a black hole. This model can explain the formation of low-mass (2–4M⊙) black holes in binary systems with optical companions. We show that the number of low-mass black holes in the Galaxy is sufficiently high for them to be detected. The population-synthesis results suggest that the vast majority of low-mass black holes are formed via the accretion-induced collapse of neutron stars. The percentage of low-mass black holes in binary systems that form due to accretion-induced collapse is 2–15% of the total number of black holes in binaries, depending on the evolutionary scenario. 相似文献
5.
The evolution of close binary systems containing Wolf-Rayet (WR) stars and black holes (BHs) is analyzed numerically. Both the stellar wind from the donor star itself and the induced stellar wind due to irradiation of the donor with hard radiation arising during accretion onto the relativistic component are considered. The mass and angular momentum losses due to the stellar wind are also taken into account at phases when the WR star fills its Roche lobe. It is shown that, if a WR star with a mass higher than ～10M ⊙ fills its Roche lobe in an initial evolutionary phase, the donor star will eventually lose contact with the Roche lobe as the binary loses mass and angular momentum via the stellar wind, suggesting that the semi-detached binary will become detached. The star will remain a bright X-ray source, since the stellar wind that is captured by the black hole ensures a near-Eddington accretion rate. If the initial mass of the helium donor is below ～5M ⊙, the donor may only temporarily detach from its Roche lobe. Induced stellar wind plays a significant role in the evolution of binaries containing helium donors with initial masses of ～2M ⊙. We compute the evolution of three observed WR-BH binaries: Cyg X-3, IC 10 X-1, and NGC 300 X-1, as well as the evolution of the SS 433 binary system, which is a progenitor of such systems, under the assumption that this binary will avoid a common-envelope stage in its further evolution, as it does in its current evolutionary phase. 相似文献
6.
A. N. Sazonov 《Astronomy Reports》2011,55(2):142-158
We present the results of WBVR observations of the low-mass X-ray binary V1341 Cyg = Cyg X-2. Our observations include a total of 2375 individual measurements
in four bands on 478 nights in 1986–1992. We tied the comparison and check stars used for the binary to the WBVR catalog using their JHK magnitudes. The uncertainty of this procedure was 3% in the B and V bands and 8%–10% for the W and R bands. In quiescence, the amplitude of the periodic component in the binary’s B brightness variations is within 0.265
m
–0.278
m
(0.290
m
–0.320
m
in W); this is due to the ellipsoidal shape of the optical component, which is distorted with gravitational forces from the X-ray
component. Some of the system’s active states (long flares) may be due to instabilities in the accretion disk, and possibly
to instabilities of gas flows and other accretion structures. The binary possesses a low-luminosity accretion disk. The light
curves reveal no indications of an eclipse near the phases of the upper and lower conjunctions in quiescence or in active
states during the observed intervals. We conclude that the optical star in the close binary V1341 Cyg = Cyg X-2 is a red giant
rather than a blue straggler. We studied the longterm variability of the binary during the seven years covered by our observations.
The optical observations presented in this study are compared to X-ray data from the Ginga observatory for the same time intervals. 相似文献
7.
We have found a mass—luminosity relation for the OB components of massive X-ray binaries that is a good estimator of the masses of these evolutionarily important binaries. Analysis of this relation showed a systematic luminosity excess of ≈1m for the OB components in these systems. No such excess was discovered for the evolutionarily related WR + O binaries, which also undergo mass exchange between their components and are the immediate precursors of X-ray binaries. A study of possible origins of the luminosity excess suggests that the most likely explanation is an X-ray luminosity related selection effect for massive X-ray binaries. Estimates show that the probability of detecting X-ray binary increases due to the enhancement of the stellar wind, which increases the efficiency of accretion by the relativistic companion while the optical component evolves along the main sequence. This can explain the magnitude of the observed luminosity excess and the position of the optical components of X-ray binaries in the luminosity—radius plane. 相似文献
8.
Results of three-dimensional numerical simulations of the gas dynamics of the envelope of the young T Tauri binary star UZ Tau E are considered. The flow structure in the circumstellar envelope of the system is analyzed. It is shown that a regime with the impulsive accretion of matter from the circumstellar disk is realized in the binary system, in which there is a periodic transfer of matter to the accretion disk of the primary component through the accretion disk of the secondary.
相似文献9.
We have fit outbursts of two X-ray novae (Nova Monocerotis 1975=A0620-00 and Nova Muscae GS 1991=1124-683) using a non-steady-state accretion-disk model. The model is based on a new solution for a diffusion-type equation for non-steady-state accretion and describes the evolution of a viscous α disk in a binary system after the peak of the outburst, when the matter in the disk is totally ionized. The accretion rate in the disk decreases according to a power law. We derive formulas for the accretion rate and effective temperature of the disk. The model has three free input parameters: the mass of the central object M, the turbulence parameter α, and the normalization parameter δt. The results of the modeling are compared with the observed X-ray and optical B and V light curves. The estimates for the turbulence parameter α are similar: 0.2–0.4 for A 0620-00 and 0.45–0.65 for GS 1124-683, suggesting a similar nature for the viscosity in the accretion disks around the compact objects in these sources. We have also derived the distances to these systems as functions of the masses of their compact objects. 相似文献
10.
V. V. Nazarenko 《Astronomy Reports》2006,50(8):647-654
We have carried out three-dimensional hydrodynamical modeling of the formation of an accretion disk around a compact object due to radiative wind of a massive donor in a close binary system. The massive X-ray binary Cen X-3, which has a precessing accretion disk and may possess relativistic jets, is considered as an example. The computations show that, when the action of the central compact object on the formation of the wind is taken into account, the radiative wind forms an accretion disk with a radius of 0.16 (in units of the orbital separation), which accretes at a rate close to 1 × 10?8 M ⊙/yr. In this model, the disk is spherically symmetrical and geometrically thick, with a tunnel going from the accretor to the upper layers of the disk along the accretor’s rotational axis at the disk center. The number density of the gas in the tunnel is five orders of magnitude lower than in the disk. The wind-disk interaction at the outer boundary of the disk produces a strong shock (wind-disk shock) directed toward the donor. The black-body emission of the disk and tunnel is nonstationary, and resembles the outbursts observed in Cen X-3. An analysis of the location of the region of nonstationary emission suggests that the outbursts occur in the wind-disk shock. 相似文献
11.
Astronomy Reports - We study the possibility that merging of a binary black hole surrounded by a circumbinary accretion disc may produce an electromagnetic response. When black holes are merging,... 相似文献
12.
V. P. Grinin 《Astronomy Reports》2002,46(5):380-389
We consider the effect of binarity of young stars on the spectral energy distribution of the IR radiation from circumstellar dust. The formation of a common dust envelope in a binary system with a low-mass secondary component is strongly affected by the disk wind from the secondary. The small velocities in peripheral areas of the wind are such that it can be partially or entirely captured by the primary, even when the distance between the components is up to several astronomical units. As a result, an envelope with a rather complex spatial and kinematic structure is formed. Its mass is many orders of magnitude smaller than that of the accretion disk around the binary. However, the thermal radiation emitted by dust particles of the envelope can be comparable to the total radiation of the accretion disk. This result is discussed in the context of the deficit at near-IR wavelengths (2–10µm) in current models for accretion disks around young stars. 相似文献
13.
A. E. Vol’vach A. M. Kutkin M. G. Larionov L. N. Vol’vach A. Lahteenmaki M. Tornikoski J. Tammi J. Léon-Tavares E. Järvelä M. F. Aller H. D. Aller 《Astronomy Reports》2013,57(1):46-51
We present an analysis of data from multi-frequency monitoring of the blazar 3C 454.3 in 2010–2012, when the source experienced an unusually prolonged flare with a duration of about two years. This corresponds to the orbital period of the companion in a scenario in which two supermassive black holes are present in the nucleus of 3C 454.3. The flare’s shape, duration, and amplitude can be explained as a result of precession, if the plane of the accretion disk and the orbital plane of the binary are coincident. We detected small-scale structure of the flare, on time scales of no more than a month. These features probably correspond to inhomogeneities in the accretion disk and surrounding regions, with sizes of the order of 1015 cm. We estimated the size of the accretion disk based on the dynamical and geometrical parameters of this binary system: its diameter is comparable to the size of the orbit of the supermassive binary black hole, and its thickness does not exceed the gravitational radius of the central black hole. The presence of characteristic small-scale features during the flare makes it possible to estimate the relative time delays of variations in different spectral ranges: from gamma-ray to millimeter wavelengths. 相似文献
14.
Under certain conditions, stars close to intermediate-mass black holes (IMBHs) can form close binary systems with these objects, in which the Roche lobe can be filled by the star and intense accretion of the star’s matter onto the IMBH is possible. Recently, accreting IMBHs have been associated with hyperluminous X-ray sources (HLXs), whose X-ray luminosities can exceed 1041 erg/s. In this paper, the evolution of star—IMBH binary systems is investigated assuming that the IMBH mainly accretes the matter of its companion star, and that the presence of gas in the vicinity of the IMBH does not appreciably affect changes in the orbit of the star. The computations take into account all processes determining the evolution of ordinary binary systems, as well as the irradiation of a star by hard radiation during the accretion of its matter onto the IMBH. The absorption of external radiation in the stellar envelope was calculated applying the same formalism that is used to calculate the opacity of the stellar matter. The computations also assumed that, if the characteristic time for the mass transfer is less than the thermal time scale of the star, there is no exchange betwween the orbital angular momentum of the system and the angular momentum of the matter flowing onto the IMBH.
Numerical simulations have shown that, under these assumptions, three types of evolution are possible for such a binary system, depending on the mass of the IMBH and the star, as well as on the star’s initial distance from the IMBH. The first type ends with the destruction of the star. For low-mass main sequence (MS) stars, only this option is realized, even in the case of large initial distances from IMBH. For massive MS stars, the star is also destroyed if the mass of the IMBH is high and the initial distance of the star from the IMBH is sufficiently small.
The second type of evolution can occur for massive MS stars, which are initially located farther from the IMBH than in the first type of evolution. In this case, the massive star fills its Roche lobe during its evolutionary expansion, after which a stage of intense mass transfer begins. It is in this phase of the evolution that the star- IMBH system can manifest itself as a HLX, when its X-ray luminosity LX exceeds 1041 erg/s for a fairly long time. Numerical simulations show that the initial mass of the donor star in systems with MBH = (103?105)M⊙ must be close to ～10 M⊙ in this case. The characteristic duration of the HLX stage is 30 000–70 000 years. For smaller initial donor masses close to ～5M⊙, LX does not reach 1041 erg/s in the stage of intense mass transfer, but can exceed 1040 erg/s. The duration of this stage of evolution is 300 000–800 000 years. A characteristic feature of this second type of evolution is an increase in the orbital period of the system over time. As a result, after a period of intense mass loss, the star “retreats” inside the Roche lobe. A remnant of the star in the form of a white dwarf is left behind, and can end up fairly far from the IMBH.
The third type of evolution can occur for massive MS stars that are initially even farther from the IMBH, as well as for massive stars that are already evolved at the initial time. In this case, conservative mass exchange in the presence of intense stellar wind leads to the star moving away from the IMBH, without filling its Roche lobe at all. For massive stars with sufficiently strong stellar winds (for example, stars with masses ～50M⊙), the accretion rate of matter onto the IMBH in this case can reach values that are characteristic of HLXs. As in the case of the second type of evolution, the stellar remnant can remain at a fairly large distance from the IMBH.
相似文献15.
The results of three-dimensional MHD numerical simulations are used to investigate the characteristic properties of the magnetic-field
structures in the accretion disks of semi-detached binary systems. It is assumed that the intrinsic magnetic field of the
accretor star is dipolar. Turbulent diffusion of the magnetic field in the disk is taken into account. The SS Cyg system is
considered as an example. The results of the numerical simulations show the intense generation of a predominantly toroidal
magnetic field in the accretion disk. Magnetic zones with well defined structures for the toroidal magnetic field form in
the disk, which are separated by current sheets in which there ismagnetic reconnection and current dissipation. Possible observational
manifestations of such structures are discussed. It is shown that the interaction of a spiral precessional wave with the accretor’s
magnetosphere could lead to quasi-periodic oscillations of the accretion rate. 相似文献
16.
Current views of the origin and evolution of single and binary stars suggest that the planets can form aroundmain-sequence
single and binary stars, degenerate dwarfs, neutron stars, and stellarmass black holes according to several scenarios. Planets
can arise during the formation of a star mainly due to excess angular momentum leading to the formation of an accretion-decretion
disk of gas and dust around a single star or the components of a binary. It is the evolution of such disks that gives rise
to planetary systems. A disk can arise around a star during its evolution due to the accretion of matter from dense interstellar
clouds of gas and dust onto the star, the accretion of mass froma companion in a binary system, and the loss of matter during
the contraction of a rapidly rotating star, in particular, if the star rotates as a rigid body and the rotation accelerates
with its evolution along the main sequence. The fraction of stars with planetary systems is theoretically estimated as 30–40%,
which is close to the current observational estimate of ∼34%. 相似文献
17.
The spin evolution of X-ray pulsars in high-mass X-ray binaries is discussed under various assumptions about the geometry and physical parameters of the accretion flow. The torque applied to the neutron star by the accretion flow and the equilibrium periods of the pulsars are estimated. It is shown that the observed spin evolution of the pulsars can be explained in a scenario in which the neutron star accretes material from a magnetized stellar wind. 相似文献
18.
We discuss characteristic features of the magnetic gas-dynamical structure of the flows in a semi-detached binary system obtained from three-dimensional simulations, assuming that the intrinsic magnetic field of the accreting star is dipolar. The turbulent diffusion of the magnetic field is taken into account. The SS Cyg system is considered as an example. Including the magnetic field can alter the basic parameters of the accretion disk, such as the accretion rate and the characteristic density. The magnetic field in the disk is primarily toroidal. 相似文献
19.
The spin-down mechanism of accreting neutron stars is discussedwith an application to one of the best studied X-ray pulsars GX301-2. We show that the maximum possible spin-down torque applied to a neutron star from the accretion flow can be evaluated as K sd (t) = ??2/(r m r cor)3/2. The spin-down rate of the neutron star in GX301-2 can be explained provided the magnetospheric radius of the neutron star is smaller than its canonical value. We calculate the magnetospheric radius considering the mass-transfer in the binary system in the frame of the magnetic accretion scenario suggested by V.F. Shvartsman. The spin-down rate of the neutron star expected within this approach is in a good agreement with that derived from observations of GX301-2. 相似文献
20.
Results of numerical modeling of the gas dynamics ofmaterial in the envelopes of T Tauri binary stars with a small component mass ratios (q = 0.08) are reported. In such systems, the less massive component is moving at a supersonic velocity, and the more massive component can move with either a subsonic or supersonic velocity. The modeling results show that the morphology of the flow changes substantially in the transition from supersonic to subsonic motion of the massive component. In particular, one of the two bow shocks vanishes, flows ofmaterial in the system are redistributed, and the characteristics of the accretion disks change. In addition, the effect of the change in the accretion mode on the evolution of the binary system and the possibility of recovering some parameters of the system from observational manifestations of shocks in the circumstellar envelope are considered. 相似文献