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1.
We present the results of spectroscopic observations of the X-ray binary V404 Cyg obtained on the 6-m telescope of the Special Astrophysical Observatory in 2001–2002. We have used a statistical approach to interpret the radial-velocity curve of V404 Cyg. We derived the dependence of the mass of the X-ray emitting component mx on the mass of the optical component mv via an analysis of the radial-velocity curve based on profiles of the CaI 6439.075 Å absorption line synthesized in a Roche model. Using the orbital inclination estimated from the ellipticity of the optical component, i=54°–64°, and the component-mass ratio q=mx/mv=16.7 found from the rotational broadening of the spectral lines, we obtain m s =10.65±1.95M⊙ for the mass of the black hole.  相似文献   

2.
We have obtained the first estimates of the masses of the components of the Her X-1/HZ Her X-ray binary system taking into account non-LTE effects in the formation of the H γ absorption line: m x = 1.8 M ⊙ and m v = 2.5 M ⊙. These mass estimates were made in a Roche model based on the observed radial-velocity curve of the optical star, HZ Her. The masses for the X-ray pulsar and optical star obtained for an LTE model lie are m x = 0.85 ± 0.15 M ⊙ and m v = 1.87 ± 0.13 M ⊙. These mass estimates for the components of Her X-1/HZ Her derived from the radial-velocity curve should be considered tentative. Further mass estimates from high-precision observations of the orbital variability of the absorption profiles in a non-LTE model for the atmosphere of the optical component should be made.  相似文献   

3.
A dynamical estimate of the mass of the black hole in the LMC X-1 binary system is obtained in the framework of a Roche model for the optical star, based on fitting of the He I 4471 Å and He II 4200 Å absorption lines assuming LTE. The mass of the black hole derived from the radial-velocity curve for the He II 4200 Å line is mx = 10.55 M⊙, close to the value found earlier based on a model with two point bodies [1].  相似文献   

4.
We have analyzed the observed radial-velocity curve for the X-ray binary M33 X-7 in a Roche model. We have analyzed the dependence between the component masses and the degree of filling of the optical star’s Roche lobe to obtain the ratio of the masses of the optical star and compact object. For the most probable mass of the optical star, m v = 70 M⊙, the mass of the compact object is m x = 15.55 ± 3.20 M⊙. It has been shown that black holes with masses of mx = 15 M⊙ and even higher can form in binaries. We present characteristic evolutionary tracks for binary systems passing through an evolutionary stage with properties similar to M33 X-7-type objects. According to population-synthesis analyses, such binaries should be present in galaxies with masses of at least 1011 M⊙. The present number of such systems in M33 should be of the order of unity. We have also studied the evolutionary status of the X-ray binary IC 10 X-1 with a Wolf-Rayet component, which may contain a massive black hole. The final stages of the evolution of the M33 X-7 and IC 10 X-1 systems should be accompanied by the radiation of gravitational waves.  相似文献   

5.
We interpret the observed radial-velocity curve of the optical star in the low-mass X-ray binary 2S 0921-630 using a Roche model, taking into account the X-ray heating of the optical star and screening of X-rays coming from the relativistic object by the accretion disk. Consequences of possible anisotropy of the X-ray radiation are considered. We obtain relations between the masses of the optical and compact (X-ray) components, m v and m x , for orbital inclinations i = 60°, 75°, and 90°. Including X-ray heating enabled us to reduce the compact object’s mass by ～0.5–1 M ⊙, compared to the case with no heating. Based on the K0III spectral type of the optical component (with a probable mass of m v ? 2.9 M ⊙), we concluded that m x ? 2.45?2.55 M ⊙ (for i = 75°?90°). If the K0III star has lost a substantial part of its mass as a result of mass exchange, as in the V404 Cyg and GRS 1905+105 systems, and its mass is m v ? 0.65?0.75 M ⊙, the compact object’s mass is close to the standard mass of a neutron star, m x ? 1.4 M ⊙ (for i = 75°?90°). Thus, it is probable that the X-ray source in the 2S 0921-630 binary is an accreting neutron star.  相似文献   

6.
The results of a systematic analysis of master radial-velocity curves for the X-ray binary 4U 1700-37 are presented. The dependence of the mass of the X-ray component on the mass of the optical component is derived in a Roche model based on a fit of the master radial-velocity curve. The parameters of the optical star are used to estimate the mass of the compact object in three ways. The masses derived based on information about the surface gravity of the optical companion and various observational data are 2.25 ?0.24 +0.23 M⊙ and 2.14 ?0.56 +0.50 M⊙. The masses based on the radius of the optical star, 21.9R⊙, are 1.76 ?0.21 +0.20 M⊙ and 1.65 ?0.56 +0.78 M⊙. The mass of the optical component derived from the mass-luminosity relation for X-ray binaries, 27.4M⊙, yields masses for the compact object of 1.41 ?0.08 + M⊙ and 1.35 ?0.18 +0.18 M⊙.  相似文献   

7.
We study the growth of the masses of neutron stars in binary systems due to the accumulation of mass from the optical donors accreted onto the neutron-star surface. Possible scenarios for this accretion are considered. The masses and magnetic-field strengths of radio pulsars derived using population-synthesis methods are compared to the observational data. The population-synthesis analysis indicates that a neutron star can increase its mass from the standard value of m x ? 1.35M⊙ to the Oppenheimer-Volkoff limit, m x ? 2.5M⊙, via accretion from a companion.  相似文献   

8.
We have performed speckle interferometry with the 6-m telescope of the Special Astrophysical Observatory and spectroscopy (at 3700–9200 Å) with the 2-m telescope at Peak Terskol of the spectroscopic and interferometric binary 9 Cyg, which is a composite-spectrum star with an orbital period of 4.3 yrs. The atmosphere of the system’s primary component is analyzed in detail. The luminosities of both components estimated to be L 1 = 103.8 L ⊙, L 2 = 55.2 L ⊙, where L ⊙ is the solar luminosity, and their effective temperatures to be T e (1) = 5300 K and T e (2) = 9400 K. The abundances of C, N, O, Fe, and other elements in the primary’s atmosphere have been derived. The chemical composition shows signatures of mixing of material from its atmosphere and the region of nuclear reactions. The evolutionary status of 9 Cyg has been determined. The binary’s age is about 400 million years; the brighter star is already in the transition to becoming a red giant, while the secondary is still in the hydrogen-burning stage near the zero-age main sequence. We suggest an evolutionary model for the binary’s orbit that explains the high eccentricity, e = 0.79.  相似文献   

9.
We present the results of our CCD photometric and moderate-dispersion spectroscopic observations of the binary system V4641 Sgr, which contains a black hole of mass ≈9.5M⊙ and a normal B9III star. The photometric light curve reveals an ellipticity effect with very high amplitudes in V and R, 0.40m and 0.37m, and the color curve shows that the surface temperature is nonuniform. All this testifies to tidal distortion of the normal star's surface due to the massive companion and to a high inclination of the orbit to the line of sight. In June and July 2002, during quiescence, we obtained data during three flares with amplitudes up to 0.26m. In particular, spectroscopic observations were acquired near the time of the black hole's inferior conjunction. One hour before conjunction, a depression by EW=0.5 Å was observed in the red wing of the Hα absorption line, interpreted as absorption by gas flowing in the direction from the observer toward the normal star. This flow is apparently associated with a rarefied gas disk around the black hole, and the conjunction grazes the stellar surface if the orbital inclination is close to 70.7°. The maximum velocity along a circular Keplerian orbit is 650 km/s at a distance of R=0.15–0.20a from the black hole (where a is the component separation). Thus, we find the mass of the black hole to be M BH =7.1–9.5M⊙, confirming the model of Orosz et al. (2001).  相似文献   

10.
We consider the evolution of close binaries in which the initial secondary component is a nondegenerate helium star with mass MHe = 0.4–60 M⊙, while the initially more massive primary has evolved into a black hole, neutron star, or degenerate dwarf. The neutron star is assumed to originate as a result of the evolution of a helium star with a mass of 2.5 M⊙ ≤ MHe ≤ 10 M⊙ after the explosion of a type Ib,c supernova. If the axial rotation of the helium star before the explosion is rigid-body and synchronized with the orbital rotation, for Porb ≤ 0.16 day, the rotational energy of the young neutron star will exceed the energy of an ordinary supernova. If the magnetic field of the neutron star is sufficiently strong, the necessary conditions for a magnetic-rotational supernova are provided. The initial rotational period of a young neutron star originating in a system with an orbital period shorter than ～50 days is shorter than ～4 s, which, according to observations, is required for the appearance of a radio pulsar. A helium star whose mass exceeds ～10 M⊙ in a close binary with an orbital period shorter than one day and with the axial rotation of the helium presupernova synchronous with the orbital rotation evolves into a Kerr black hole, whose formation is likely to be accompanied by a gamma-ray burst with a duration longer than two seconds. In particular, we consider close binaries in which the second supernova results in the formation of a neutron star that remains in the binary. The theoretical distribution of orbital periods and eccentricities for such systems is consistent with that observed for radio pulsars in the Galactic disk in binaries with compact components and orbital eccentricities exceeding ～0.09, providing an explanation for the observed correlation between the orbital eccentricities and orbital periods for these systems.  相似文献   

11.
We have analyzed the broad-band light curve of the massive eclipsing binary BAT99-129, which is located in the Large Magellanic Cloud and consists of WN3(h) and O5V components. The light curve was obtained as part of the MACHO project. The dense extended atmosphere of the Wolf-Rayet (WR) star makes it impossible to apply a standard parametric model, such as that of Wilson and Devinney, to analyze the light curve. We reconstructed the distributions of the brightness and absorption across the disk of the WR component by directly solving the integral equations describing the eclipses in the system. Our analysis yields reliable estimates of the system’s orbital parameters and the parameters of its components. The orbital inclination is 78°, the size of the orbit 28.5 R ⊙, and the radius of the O component R O = 7.1 R ⊙. The size of the WR core, which is opaque in the optical continuum, is R WR = 3.4 R ⊙, and the brightness temperature at the center of the WR-component disk is T br = 45 000 K. We discuss possible uncertainties in the parameters obtained. The derived information is used to draw conclusions about the system’s evolutionary status.  相似文献   

12.
Modern modeling of the population of low-mass X-ray binary systems containing black holes applying standard assumptions leads to a lack of agreement between the modeled and observed mass distributions for the optical components, with the observed masses being lower. This makes the task of estimating the systematic errors in the derived component masses due to imperfect models relevant. To estimate the influence of systematic errors in the derived masses of stars in X-ray binary systems, we considered two approximations for the tidally deformed star in a Roche model. Approximating the star as a sphere with a volume equal to that of the Roche lobe leads to slight overestimation of the equatorial rotational velocity V rot sin i, and hence to slight underestimation of the mass ratio q = M x /M v . Approximating the star as a flat, circular disk with constant local line profiles and a linear limb-darkening law (a classical rotational broadeningmodel) is an appreciably cruder approach, and leads to overestimation of V rot sin i by about 20%. In the case of high values of q = M x /M v , this approximation leads to substantial underestimation of the mass ratio q, which can reach several tens of percent. The mass of the optical star is overestimated by a factor of 1.5 in this case, while the mass of the black hole is changed only slightly. Since most estimates of component mass ratios for X-ray binary systems are carried out using a classical rotational broadening model for the lines, this leads to the need for appreciable corrections to (reductions of) previously published masses for the optical stars, which enhances the contradiction with the standard evolutionary scenario for low-mass X-ray binaries containing black holes.  相似文献   

13.
The paper analyzes the mass distribution of stellar black holes derived from the light and radial-velocity curves of optical stars in close binary systems using dynamical methods. The systematic errors inherent in this approach are discussed. These are associated primarily with uncertainties in models for the contribution from gaseous structures to the optical brightness of the systems under consideration. The mass distribution is nearly flat in the range 4–15M ⊙. This is compared with the mass distribution for black holes in massive close binaries, which can be manifest as ultrabright X-ray sources (L x >1039 erg/s) observed in other galaxies. If the X-ray luminosities of these objects correspond to the Eddington limit, the black-hole mass distribution should be described by a power law, which is incompatible with the flat shape derived dynamically from observations of close binaries in our Galaxy. One possible explanation of this discrepancy is the rapid evaporation of stellar-mass black holes predicted in recent multi-dimensional models of gravity. This hypothesis can be verified by refining the stellar black-hole mass spectrum or finding isolated or binary black holes with masses below ～3M ⊙.  相似文献   

14.
We present the results of our IR photometric observations of the classical symbiotic star BF Cyg acquired in 1978–2003. The variability range in the J and K bands was ～0.2m. A periodic component in the cool star’s brightness variations is clearly visible, its period being half the orbital one and its J amplitude being ～0.15m. This component is associated with the ellipsoidal shape of the red giant, which model calculations show fills its Roche lobe. This is required in order to reproduce ellipsoidal brightness variability with such a large amplitude: the calculated amplitude for a red giant filling 90% of its Roche lobe is half the observed value. At the same time, it was not possible to confidently chose the optimum component-mass ratio, q = M giant /Mhot, and orbital inclination, i, from possible values in the ranges q = 2–4, i = 70°–90°. Including the contribution from the hot radiation sources (the hot component and ionized envelope), which vary with a period equal to the orbital period, has a considerable influence on the estimated parameters associated with the red giant’s ellipsoidal brightness variations, and this contribution cannot be neglected. The deviations of the observed from the calculated light curve are irregular, with the rms deviation being σ(O-C) ≈ 0.04m.  相似文献   

15.
We have analyzed the orbital light curve of the X-ray nova XTE J1118+480 in a “disk + hot line” model based on three-dimensional gas-dynamical computations of gas flows in interacting binary systems. As a result, we have been able to derive reliable parameters for the system: i = 80 ?4 +4 degrees, MBH = 7.1 ?0.1 +0.5 M⊙, M opt = 0.39 ?0.07 +0.15 M⊙.  相似文献   

16.
The results of infrared observations of the two Be stars X Per and V725 Tau, which are the optical components of X-ray binary systems, obtained in 1994–2016 are presented. The observations cover Be-star phases as well as shell phases. The data analysis shows that the radiation observed from the binaries at 1.25, 3.5, and 5 μm can be explained as the combined radiation from the optical components and variable sources (shells/disks) that emit as blackbodies (BBs). Emission from a source with the color temperature T c ~1000?1500 K was detected for X Per at λ ≥ 3.5 μm. The highest IR-brightness variation amplitudes for X Per were 0.9?1.2 m (JHK magnitudes) and ~1.45 m (LM magnitudes); for V725 Tau, they were 1.1?1.4 m and ~1.7 m (L magnitudes). The parameters of the optical components and interstellar extinction during the Be phases were estimated: the color excesswasE(B?V) = 0.65±0.08 m and 0.77 ± 0.03 m for X Per and V725 Tau, respectively. Light from the variable sources (disks/shells) was distinguished and their color temperatures, radii, and luminosities estimated for different observation epochs in a BB model. The variations of the binaries’ IR brightness and colors are shown to be due to changing parameters of the variable sources. The mean color temperature of the cool source (disk/shell) and the mean radius and mean luminosity of X Per are 9500± 2630 K, (35 ± 10) R⊙, and (9100± 540) L⊙. For V725 Tau, these parameters are 6200 ± 940 K, (27 ± 6) R⊙, and (980 ± 420) L⊙. The 1.25–5 μm radiation from X Per at different epochs can be represented as a sum of contributions from at least three sources: the optical component and two objects emitting as BBs. To reproduce the 1.25–3.5 μm radiation from V725 Tau, two components are sufficient: the optical component and a single variable BB object. For both binary systems, orbital variations of the IR brightness can be noted near the Be-star phase. The amplitudes of the J-band variations of X Per and V725 Tau are about 0.3 m and 0.1 m , respectively.  相似文献   

17.
The results of a 3D Doppler tomography analysis for the X-ray binary system Cyg X-1 in the HeII λ 4686 Å line are presented. Information about the motions of gaseous flows outside the orbital plane has been obtained for the first time. Line profiles obtained in June 2007 on the 2-m telescope of the Terskol Branch of the Institute of Astronomy (Russia) and on the 2.1-m telescope of the National Astronomical Observatory of Mexico were used. A detailed analysis of these spectral data is presented: the distribution of the data in time, distribution of orbital phases for the projections, comparison of the line profile shapes for the data from two observatories. The geometry of the total transfer function obtained in the reconstruction is considered. The possibility of applying the profiles obtained to realize 3D tomography is justified. The resolution of the constructed 3D tomogram in velocity space is 60 × 60 × 40 km/s for V x , V y , V z . Fifteen cross sections for 15 different V z values perpendicular to the orbital plane are presented. The intensity distributions corresponding to the velocities of gaseous structures in the binary system are obtained. The reconstruction was realized using the radio-astronomical approach, developed for solving problems in tomography with a limited number of projections.  相似文献   

18.
Variations of the orbital periods of the eclipsing binaries TU Cnc, VZ Leo, and OS Ori are analyzed. Secular period decreases were earlier believed to occur in these systems. It is demonstrated that the period variations of TU Cnc can be represented using the light-time effect corresponding to the orbital motion of the eclipsing binary with a period of 78.6 years around the center ofmass of the triple system, with the mass of the third body being M 3 > 0.82M ⊙. With the same accuracy, the period variations of VZ Leo and OS Ori can be represented either solely using the light-time effect, or a superposition of a secular period decrease and the light-time effect. For VZ Leo, the period of the long-term orbit is 63.8 years in the former case and 67.9 years in the latter case. Similar masses for the third body are indicated in both cases: M 3 > 0.55M ⊙ and M 3 > 0.61M ⊙. For OS Ori, the period of the long-term orbit is 46 years and M 3 > 0.5M ⊙ in the former case, and the period is 36 years and M 3 > 0.6M ⊙ in the latter case.  相似文献   

19.
We have carried out a search for low-surface-brightness dwarf galaxies in the region of the Leo-I Group (M96) in images of the second Palomar Sky Survey. We found a total of 36 likely dwarf members of the group with typical magnitudes B t ～18m–19m in an area of sky covering 120 square degrees. Half of these galaxies are absent from known catalogs and lists of galaxies. The radial-velocity dispersion calculated for 19 galaxies is 130 km/s. The Leo-I Group has a mean distance from the Sun of 10.4 Mpc, a mean projected radius of 352 kpc, an integrated luminosity of 6.7 × 1010L⊙, a virial mass-to-luminosity ratio of 107 M⊙/L⊙, and a mean crossing time of 2.7 Gyr. The group shows evidence for a radial segregation of the galaxies according to morphological type and luminosity, suggesting that the group is in a state of dynamical relaxation. The subsystem of bright galaxies in the Leo-I Group is smaller in size (250 kpc) and has a lower velocity dispersion (92 km/s), resulting in a lower virial mass-to-luminosity ratio (34 M⊙/L⊙), as is typical of the Local Group and other nearby groups of galaxies.  相似文献   

20.
Orbital-period variations of the eclipsing binaries FK Aql and FZ Del are analyzed. For each of the systems, a superposition of two cyclic variations of their orbital periods is found. FK Aql may be a quadruple system that contains two more bodies, besides the eclipsing binary, with masses M 3 ? 1.75M ⊙ and M 4 ? 1.47M ⊙, and the corresponding periods 15 and 82 yrs. This could also be a triple system with a third body of mass M 3 ? 1.75M ⊙ and a period of the long-period orbit P 3 = 15 yrs, or with a third body of mass M 3 ? 1.30M ⊙ and a period of the long-period orbit P 3 = 82 yrs. FZ Del may be a quadruple system with the additional componentmasses M 3 ? 0.2M ⊙ and M 4 ? 0.3M ⊙, with the periods 10.2 and 53.7 yrs. This could also be a triple system with a third-body mass M 3 ? 0.2M ⊙ and a period of the long-period orbit P 3 = 10.2 yrs. In both systems, the residual period variations could be due to magnetic cycles of the secondary. The period variations of the eclipsing binary FZ Del could also be due to apsidal motion, together with the influence of a third body or the effects of magnetic activity.  相似文献   

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