首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
We derive the parameters of the hot, massive close binary system UU Cas from earlier and recent photoelectric UBVR observations: M 1 = 34.5M ⊙, M 2 = 25.7M ⊙, A = 69R ⊙, and i=68°; the components' limb darkening coefficients are close to 1. Our fitting of the light curves provides evidence for a high degree of over-contact: the components fill their inner critical surfaces by 132% and 100%. It is possible that the appearance of the light curve is determined not only by the distorted shapes of the components and their eclipses but, to a considerable extent, by screening by a complex envelope and the envelope's contribution to the system's total luminosity.  相似文献   

2.
We have obtained high-accuracy photoelectric measurements of ES Lac, an eclipsing binary with an elliptical orbit (B9III + B9III; P = 4.459d, e = 0.198) in 1985–2004 at the Sternberg Astronomical Institute’s Tien Shan High-Altitude Observatory. Our detailed analysis of the 19-year uniform series of measurements has yielded the first photometric elements for this system, as well as a self-consistent set of physical and geometrical parameters for the binary. The virtually identical components (M 1 = M 2 = 3.0 M ⊙; R 1 = R 2 = 4.12 R ⊙) are appreciably separated from the main sequence, and are located on the giant branch: their age is t = (3.5 ± 0.2) × 108 yrs. An analysis of our observations together with previously published times of minima has enabled a considerable refinement of the period of the apsidal motion, U = 355 ± 20 years, and a first determination of the apsidal parameter reflecting the radial density distributions for the components stars: k 2 obs = 0.00213(18). This value is in a good agreement with the value expected theoretically for current evolutionary models of such stars: k 2 th = 0.00257(15).  相似文献   

3.
Our analysis of a 22-year uniform series of photoelectric U BV measurements of HS Her, started in 1969–1983 by D.Ya. Martynov and completed by us in 1984–1991, enabled us to determine new times of minima and revise some times of minima published earlier. Combined with other published data, this information can be used to improve the system’s apsidal elements: U obs = (89.7 ± 5.1) years and log-k 2 obs = ?2.33(4), testifying to a somewhat stronger concentration of matter towards the center than is predicted by current models for main-sequence stars (log -k 2 th = ?2.21). This provides additional evidence that the system’s secondary is at the pre-main-sequence stage of evolution, as we suggested earlier based on our analysis of the system’s photometric elements. We confirm the presence of a third body in the system in a long-period eccentric orbit, as was first suggested in 2002 by Wolf et al. However, in contrast to the results of that paper, we demonstrate that the currently available observational data are insufficient to reliably determine this orbit’s parameters. We estimate the mass of the third body to be M 3 = (1.0?2.0)M ⊙ for M 1 = 5M ⊙ and M 2 = 1.6 M ⊙.  相似文献   

4.
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   

5.
We have studied the time behavior of the orbital period and the primary’s pulsation period for the eclipsing binary system Y Cam, whose secondary fills its Roche lobe and whose primary is a δ Scuti star. The times of minima available for this eclipsing binary cover 120 years. δ Scuti pulsations of the primary have been observed over the last 50 years, with the period of these pulsational brightness variations remaining virtually unchanged during the entire observed time interval. The large-amplitude cyclic variations of the orbital period of Y Cam cannot be explained solely by the presence of a third body in the system. It is possible to explain the period variations of Y Cam with magnetic oscillations or a superposition of a stationary matter flow from the lower-mass to the higher-mass component together with magnetic oscillations, similar to the case of AB Cas. A good agreement with observations is provided by a model assuming a stationary matter flow from the secondary filling its Roche lobe to the primary, at the rate of 2.85 × 10?7 M ⊙/year, superposed with irregular period jumps that can be explained by instabilities in the matter flow. We have detected cyclic variations of the orbital period of Y Cam with an amplitude of 0.011d, which can be understood if the binary moves in a long-period orbit (with a period of 38.6 years) around a third body with mass M 3 s> 0.30M ⊙. These cyclic period variations of the eclipsing binary agree with the observed small period variations of the δ Scuti pulsations.  相似文献   

6.
We present the results of long-term (1978–1998) infrared and optical observations of the unique symbiotic system CH Cygni. The system’s IR brightness and color variations are generally consistent with a model in which the source is surrounded by a dust envelope with variable optical depth. There was evidence for a hot source in the CH Cyg system during the entire period from 1978 to 1998, with the exception of several hundred days in 1987–1989. Over the observation period, there was tendency for the system to gradually redden at 0.36–5 µm, accompanied by a brightness decrease at 0.36–2.2µm and a brightness increase at 3.5 and 5 µm. The “activation” of the cool sources in 1986–1989 nearly coincided with the disappearance of radiation from the hot source. The dust envelope of CH Cyg is not spherically symmetrical, and its optical depth along the line of sight is substantially lower than its emission coefficient, the mean values being τex(L)～0.06 and τem(L)～0.16. We confirm the presence of a 1800-to 2000-day period in both the optical and IR, both accounting for, and not accounting for, a linear trend. The spectral type of the cool star varied between M5III and M7III. The spectral type was M5III during the phase of maximum activity of the system’s hot source, while the spectral type was M7III when the star’s optical radiation was almost completely absent. The luminosity of the cool giant varied from (6300–9100)L ⊙; its radius varied by approximately 30%. The ratio of the luminosities of the dust envelope and the cool giant varied from 0.08 to 0.5; i.e., up to 50% of the cool star’s radiation could be absorbed in the envelope. The temperature of dust particles in the emitting envelope varied from 550 to 750 K; the radius of the envelope varied by more than a factor of 2. The expansion of the emitting dust envelope observed in 1979–1988 accelerated: its initial velocity (in 1979) was ～8 km/s, while the maximum velocity (in 1987–1989) was ～180 km/s. Beginning in 1988, the radiation radius of the dust envelope began to decrease, first at ～45 km/s and then (in 1996–1998) at ～3 km/s. From 1979 until 1996, the mass of the emitting dust envelope increased by approximately a factor of 27 (the masses in 1979 and 1988 were ～1.4×10?7 M ⊙ and ～3.8×10?6 M ⊙, respectively), after which (by 1999) it decreased by nearly a factor of 7. The mass-loss rate of the cool star increased in 1979–1989, reaching ～3.5×10?6 ～3.5×10?6 M ⊙/yr in 1988. Subsequently (up to the summer of 1999), the envelope itself began to lose mass at a rate exceeding that of the cool star. The largest input of matter to the envelope occurred after the phase of optical activity in 1978–1985. If the envelope’s gas-to-dust ratio is ～100, the mass of matter ejected in 1988 was ～4×10?4 M ⊙.  相似文献   

7.
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   

8.
The results of hydrodynamical calculations of radially pulsating helium stars with masses 0.5M⊙≤M≤0.9M⊙, bolometric luminosities 600L⊙≤5×103L⊙, and effective temperatures 1.5×104 K≤Teff≤3.5×104 K are presented. The pulsation instability of these stars is due to the effects of ionization of iron-group elements in layers with temperatures T～2×105 K. The calculations were carried out using opacities for the relative mass abundances of hydrogen and heavy elements X=0 and Z=0.01, 0.015, and 0.02. Approximate formulas for the pulsation constant Q over the entire range of pulsation instability of the hot helium stars in terms of the mass M, radius R, effective temperature Teff, and heavy-element abundance Z are derived. The instability of BX Cir to radial pulsations with the observed period Π=0.1066 d occurs only for a mass M≥0.55M⊙, effective temperature Teff≥23000 K, and heavy-element abundance Z≥0.015. The allowed mass of BX Cir is in the range 0.55M⊙≤M≤0.8M⊙, which corresponds to luminosities 800L⊙≤M≤1400L⊙ and mean radii 1.7R⊙?R?2.1R⊙.  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 have obtained the first U BV R photoelectric light curves for a recently discovered eclipsing binary with a period of 9.33 d and an appreciable eccentricity (e = 0.08). We have used these data to determine the photometric elements of the system for a model with two spherical stars with linear limb darkening. The high accuracy of the observations enabled determination of the absolute parameters of the components using available calibrations. The masses of the components are 1.28 and 1.08 M ⊙, and their ages are two billion years. The present orientation of the orbital ellipse is unfavorable for studies of the apsidal rotation, which is essentially due to relativistic effects.  相似文献   

11.
The observed properties of Wolf-Rayet stars and relativistic objects in close binary systems are analyzed. The final masses M CO f for the carbon-oxygen cores of WR stars in WR + O binaries are calculated taking into account the radial loss of matter via stellar wind, which depends on the mass of the star. The analysis includes new data on the clumpy structure of WR winds, which appreciably decreases the required mass-loss rates $\dot M_{WR}$ for the WR stars. The masses M CO f lie in the range (1–2)M ⊙–(20–44)M ⊙ and have a continuous distribution. The masses of the relativistic objects M x are 1–20M ⊙ and have a bimodal distribution: the mean masses for neutron stars and black holes are 1.35 ± 0.15M ⊙ and 8–10M ⊙, respectively, with a gap from 2–4M ⊙ in which no neutron stars or black holes are observed in close binaries. The mean final CO-core mass is $\overline M _{CO}^f = 7.4 - 10.3M_ \odot$ , close to the mean mass for the black holes. This suggests that it is not only the mass of the progenitor that determines the nature of the relativistic object, but other parameters as well-rotation, magnetic field, etc. One SB1R Wolf-Rayet binary and 11 suspected WR + C binaries that may have low-mass companions (main-sequence or subgiant M-A stars) are identified; these could be the progenitors of low-mass X-ray binaries with neutron stars and black holes.  相似文献   

12.
Three-dimensional (3D) numerical models of close binaries are used to study the structure and dynamics of common envelopes formed due to periodic ejections of matter from the accretion disk through the vicinity of the Lagrange point L3. The results are used to estimate the physical parameters of the envelope, including its 3D matter distribution, and the matter-flow configuration and dynamics. Possible observational manifestations of such envelopes are estimated. We present the envelope’s radialvelocity distributions at various phases and times, as well as model light curves taking into account extinction in the envelope. The envelope becomes optically thick for systems with high mass-exchange rates, ? > 10?8 M ⊙/year, and has a significant influence on the binary’s observed features. The uneven phase distributions of the matter and density variations due to periodic injections of matter into the envelope are important for interpretations of observations of close binary stars.  相似文献   

13.
  相似文献   

14.
A long series of observations of the low-mass eclipsing system CM Dra (M 1, M ⊙<0.25M ⊙, dM4.5e, V=12.9m, P orb=1.27d) was obtained in 1996–1997 as part of the international TEP (Search for Transits of Extrasolar Planets) project. The observations were obtained on the 70-cm telescope of the Astronomical Observatory of Ural State University with an automatic two-star photometer. The total duration of the data series was 155 h. We construct and analyze a master light curve, including calculation of the photometric and absolute orbital elements. Evidence for surface activity was detected. The light curve of CM Dra outside eclipses shows low-amplitude (0.024m) brightness variations, suggesting the presence of a starspot on one of the components. The amplitude of these variations stayed the same over 20 years, but the phase of the brightness maximum shifted by one-third of the orbital period, possibly reflecting changes in the longitude or asymmetry of a single large polar spot. We detected four flares whose energies were factors of several hundred higher than those of solar flares. The derived flare rate agrees with data for CM Dra in the literature but is much lower than is typical for Population I stars in our Galaxy.  相似文献   

15.
A brief review of the observed parameters of binary systems with black holes is presented. We discuss in detail the evolutionary status of the X-ray binary GRS 1915+105, which contains a massive black hole. Numerical simulations of the evolution of GRS 1915+105 at the X-ray stage indicate that the most probable initial mass of the optical component (donor star) is (1.5–)M⊙. Two possible scenarios are suggested for the evolution of the system prior to the formation of the black hole. If the initial mass of the optical component was (2.5–)M⊙, the system underwent a common-envelope phase; in this case, the initial mass of the black hole progenitor did not exceed ～50M⊙. If the initial mass of the donor was (1.5–2.5)M⊙, a scenario without a common envelope is possible, with the initial mass of the black hole progenitor being smaller than ～50M⊙. The lack of information about the initial mass-ratio distribution for binary components for small q and the uncertainty of the system parameters make it impossible to give preference to a particular scenario for the system's prior evolution.  相似文献   

16.
A detailed study of variations of the orbital periods of the Algol-type eclipsing binary systems RZ Cas and Z Dra is presented. The fairly complex variations of the periods of both systems can be represented as a superposition of a secular increase of the period, slow periodic fluctuations, and quasiperiodic oscillations with a small amplitude occurring on timescales of decades. The secular increase of the period can be explained by the steady mass transfer from the less massive to the more massive component with conservation of the total angular momentum. The mass-transfer rate is 5.7 × 10?9M⊙/yr for RZ Cas and 3.0×10?8M⊙/yr for Z Dra. To explain the long-period cyclic variations of the orbital periods of RZCas and Z Dra, it must be assumed that the eclipsing binaries move in long-period orbits. RZ Cas moves with a period of 133 yr around a third body withmass M3 > 0.55M⊙, while Z Dra moves with a period of 60 yr around a third body with mass M3 > 0.7M⊙. The residual fluctuations of the periods may be due to a superposition of variations due to magnetic cycles and non-stationary ejections of matter.  相似文献   

17.
The formation and evolution of supermassive (102?1010 M ⊙) black holes (SMBHs) in the dense cores of globular clusters and galaxies is investigated. The raw material for the construction of the SMBHs is stellar black holes produced during the evolution of massive (25?150M ⊙) stars. The first SMBHs, with masses of ～1000M ⊙, arise in the centers of the densest and most massive globular clusters. Current scenarios for the formation of SMBHs in the cores of globular clusters are analyzed. The dynamical deceleration of the most massive and slowly moving stellar-mass (< 100M ⊙) black holes, accompanied by the radiation of gravitational waves in late stages, is a probable scenario for the formation of SMBHs in the most massive and densest globular clusters. The dynamical friction of the most massive globular clusters close to the dense cores of their galaxies, with the formation of close binary black holes due to the radiation of gravitational waves, leads to the formation of SMBHs with masses ? 103 M ⊙ in these regions. The stars of these galaxies form galactic bulges, providing a possible explanation for the correlation between the masses of the bulge and of the central SMBHs. The deceleration of the most massive galaxies in the central regions of the most massive and dense clusters of galaxies could lead to the appearance of the most massive (to 1010 M ⊙) SMBHs in the cores of cD galaxies. A side product of this cascade scenario for the formation of massive galaxies with SMBHs in their cores is the appearance of stars with high spatial velocities (> 300 km/s). The velocities of neutron stars and stellar-mass black holes can reach ～105 km/s.  相似文献   

18.
Spectrophotometric observations are used to study the envelopes of the FeII nova V2467 Cyg and the HeN nova V2491 Cyg. The abundances of several elements in the nova envelopes and the envelope masses are estimated. The nitrogen mass abundance in the V2467 Cyg envelope is higher than the solar value by a factor of 186 and the oxygen abundance by the factor of 10. The nitrogen abundance in the envelope of V2491 Cyg exceeds the solar value by a factor of 56, the oxygen abundance by a factor of 12, and the neon abundance by a factor of 8. The masses of the envelopes were estimated to be 8.5×10?5 M ⊙ for V2467 Cyg and 1.5×10?5 M ⊙ for V2491 Cyg. These envelope elemental abundances and masses are in good agreement with those of low-mass CO white dwarfs (0.8 M ⊙) and ONe white dwarfs (1.15 M ⊙).  相似文献   

19.
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   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号