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1.
Run-Qian Huang Han-Feng Song Shao-Lan Bi National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming Graduate University of Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(2):235-244
Three importantphysical processes occurringin contact binarysystems are studied. The first one is the effect of spin, orbital rotation and tide on the structure of the components, which includes also the effect of meridian circulation on the mixing of the chemical elements in the components. The second one is the mass and energy exchange between the components. To describe the energy exchange, a new approach is introduced based on the understanding that the exchange is due to the release of the potential, kinetic and thermal energy of the exchanged mass. The third is the loss of mass and angular momentum through the outer Lagrangian point. The rate of mass loss and the angular momentum carried away by the lost mass are discussed. To show the effects of these processes, we follow the evolution of a binary system consisting of a 12M and a 5M star with mass exchange between the components and mass loss via the outer Lagrangian point, both with and without considering the effects of rotation and tide. The result shows that the effect of rotation and tide advances the start of the semi-detached and the contact phases, and delays the end of the hydrogen-burning phase of the primary. Furthermore, it can change not only the occurrence of mass and angular momentum loss via the outer Lagrangian point, but also the contact or semi-contact status of the system. Thus, this effect can result in the special phenomenon of short-term variations occurring over a slow increase of the orbital period. The occurrence of mass and angular momentum loss via the outer Lagrangian point can affect the orbital period of the system significantly, but this process can be influenced, even suppressed out by the effect of rotation and tide. The mass and energy exchange occurs in the common envelope. The net result of the mass exchange process is a mass transfer from the primary to the secondary during the whole contact phase. 相似文献
2.
By calculating the angular momentum transport during the evolution of a binary system, the variations of the rotational and revolution periods of the binary system under the tidal action, as well as the tidal effect on the evolution of the system are investigated. The calculated results indicate that when a close binary system evolves in the main sequence, the tidal friction will make the rotation and revolution approach to a closed state in a short time, but it takes a long time to attain a complete synchronization. After mass exchange started, the synchronous rotation can be changed more easily into the non-synchronous rotation for the semi-detached binaries. But for the contact binaries, the mass exchange is not strong enough to break the synchronization. The evolutionary tracks of the synchronization and non-synchronization models in the HR diagram are also compared with each other, and the result shows that for the non-synchronization model, the evolutionary curve of the primary star moves toward the direction of high luminosity and high effective temperature on the HR diagram at the mass exchange stage. Finally, by analyzing the statistical data of observations, it is found that the observed fact that the non-synchronous rotation exists in a period even longer than the tide-locking timescale can be explained by this model. 相似文献
3.
通过计算双星演化中的角动量转移,研究了潮汐作用下双星系统自转与公转周期的变化以及潮汐作用对双星演化的影响.结果表明,密近双星系统在主序演化时,潮汐摩擦会在较短的时间内使自转与公转达到比较接近的状态,此后经过一个较长时间的调整才能使自转与公转达到同步转动.物质交换阶段开始后,半相接双星系统更容易出现非同步转动,而相接双星系统物质交换很难破坏系统的同步状态.同时比较了非同步双星模型与同步双星模型演化曲线在赫罗图上的不同,结果表明非同步模型在物质交换阶段主星演化曲线向赫罗图光度和有效温度高的方向移动.最后通过对统计的观测数据进行分析后发现,采用该模型可以解释观测上双星超过潮汐锁定时标后仍然存在非同步转动的现象. 相似文献
4.
5.
A photoelectric light curve of BL And is presented along with the first CCD light curve of GW Tau. Both objects are short-period eclipsing binaries and were observed in 2003 or 2004. Photometric elements were computed using the latest version of the Wilson–Van Hamme code. The results reveal that BL And is a semidetached system with the primary component filling its Roche lobe and the secondary one almost filling but still detached, while GW Tau is a marginal-contact binary system with a small degree of contact ( f = 10.9 per cent) and a large temperature difference of about 3100 K. All available eclipse times, including new ones, were analysed for each system. It was found that the orbital period of BL And is decreasing at the rate of d P /d t =−2.36 × 10−8 (±0.09) d yr−1 while that of GW Tau may be decreasing or oscillating. We think period decrease is more probable. The derived configuration and secular period decrease for BL And combined with the asymmetry of the light curve indicate that this system may evolve from the present semidetached phase into a contact stage, with mass transfer from the primary component to the secondary one through the L 1 point, or that it might just undergo the broken stage predicted by the theory of thermal relaxation oscillations. In contrast, GW Tau is a marginal-contact binary in poor thermal contact and may be at the beginning of the contact phase. 相似文献
6.
We describe the present state of massive star research seen from the viewpoint of stellar evolution, with special emphasis
on close binaries. Statistics of massive close binaries are reasonably complete for the Solar neighbourhood. We defend the
thesis that within our knowledge, many scientific results where the effects of binaries are not included, have an academic
value, but may be far from reality. In chapter I, we summarize general observations of massive stars where we focus on the
HR diagram, stellar wind mass loss rates, the stellar surface chemistry, rotation, circumstellar environments, supernovae.
Close binaries can not be studied separately from single stars and vice versa. First, the evolution of single stars is discussed
(chapter I). We refer to new calculations with updated stellar wind mass loss rate formalisms and conclusions are proposed
resulting from a comparison with representative observations. Massive binaries are considered in chapter II. Basic processes
are briefly described, i.e. the Roche lobe overflow and mass transfer, the common envelope process, the spiral-in process
in binaries with extreme mass ratio, the effects of mass accretion and the merging process, the implications of the (asymmetric)
supernova explosion of one of the components on the orbital parameters of the binary. Evolutionary computations of interacting
close binaries are discussed and general conclusions are drawn. The enormous amount of observational data of massive binaries
is summarized. We separately consider the non-evolved and evolved systems. The latter class includes the semi-detached and
contact binaries, the WR binaries, the X-ray binaries, the runaways, the single and binary pulsars. A general comparison between
theoretical evolution and observations is combined with a discussion of specially interesting binaries: the evolved binaries
HD 163181, HD 12323, HD 14633, HD 193516, HD 25638, HD 209481, Per and Sgr; the WR+OB binary V444 Cyg; the high mass X-ray binaries Vela X-1, Wray 977, Cyg X-1; the low mass X-ray binaries Her
X-1 and those with a black hole candidate; the runaway Pup, the WR+compact companion candidates Cyg X-3, HD 50896 and HD 197406. We finally propose an overall evolutionary model
of massive close binaries as a function of primary mass, mass ratio and orbital period. Chapter III deals with massive star
population synthesis with a realistic population of binaries. We discuss the massive close binary frequency, mass ratio and
period distribution, the observations that allow to constrain possible asymmetries during the supernova explosion of a massive
star. We focuss on the comparison between observed star numbers (as a function of metallicity) and theoretically predicted
numbers of stellar populations in regions of continuous star formation and in starburst regions. Special attention is given
to the O-type star/WR star/red supergiant star population, the pulsar and binary pulsar population, the supernova rates.
Received 17 July 1998 相似文献
7.
CCD photometry of the short-period binary stars KQ Gem and V412 Her is presented, together with some spectroscopic observations of KQ Gem. Although both systems are classified in the General Catalogue of Variable Stars as having light curves of EB/KW type, our data and analyses, involving light-curve synthesis and stellar surface imaging, show that KQ Gem is an EB system that is in marginal contact and has an enhanced bright region around the substellar point on the secondary component, whilst V412 Her is an EW system, a true contact binary with a mass ratio of 0.46 and both stars having the same surface brightness. The properties of the components of the two systems are compared with other marginal-contact and contact binaries, and a plea is repeated for more theoretical work on the mass/energy interchanges in contact binaries. 相似文献
8.
Shengbang Qian† 《Monthly notices of the Royal Astronomical Society》2001,328(3):914-924
Orbital period changes of ten contact binary systems (S Ant, ε CrA, EF Dra, UZ Leo, XZ Leo, TY Men, V566 Oph, TY Pup, RZ Tau and AG Vir) are studied based on the analysis of their curves. It is discovered that the periods of the six systems, S Ant, ε CrA, EF Dra, XZ Leo, TY Men and TY Pup, show secular increases. For UZ Leo, its secular period increase rate is revised. For the three systems, V566 Oph, RZ Tau and AG Vir, weak evidence is presented that a periodic oscillation (with periods of 20.4, 28.5 and 40.9 yr respectively) is superimposed on a secular period increase. The cyclic period changes can be explained by the presence of an unseen third body in the three systems. All the sample stars studied are contact binaries with .
Furthermore, orbital period changes of 27 hot contact binaries have been checked. It is found that, apart from AW UMa with the lowest mass ratio , none shows an orbital period decrease. The relatively weak magnetic activity in the hotter contact binaries means little angular momentum loss (AML) from the systems via magnetic stellar winds. The period increases of these W UMa binaries can be explained by mass transfer from the secondary to the primary components, which is in agreement with the prediction of the thermal relaxation oscillation (TRO) models. This suggests that the evolution of a hotter W UMa star is mainly controlled by TRO. On the other hand, for a cooler W UMa star , its evolution may be TRO plus AML, which coincides with the recent results of Qian. 相似文献
Furthermore, orbital period changes of 27 hot contact binaries have been checked. It is found that, apart from AW UMa with the lowest mass ratio , none shows an orbital period decrease. The relatively weak magnetic activity in the hotter contact binaries means little angular momentum loss (AML) from the systems via magnetic stellar winds. The period increases of these W UMa binaries can be explained by mass transfer from the secondary to the primary components, which is in agreement with the prediction of the thermal relaxation oscillation (TRO) models. This suggests that the evolution of a hotter W UMa star is mainly controlled by TRO. On the other hand, for a cooler W UMa star , its evolution may be TRO plus AML, which coincides with the recent results of Qian. 相似文献
9.
Photometric data on FG Hya obtained in 2002 and 2004 are presented. Three data sets show the exchange between A-type, W-type and the variable O'Connell effects. The photometric mass ratio ( q = 0.1115 ± 0.0003) derived from B and V light curves is almost the same as the spectroscopic mass ratio ( q sp = 0.112 ± 0.004) . The new photometric solutions reveal that FG Hya is a deep overcontact binary system ( f = 85.6 ± 1.8 per cent) with a spotted massive component. A period investigation, based on all available photoelectric or CCD times of light minimum, shows that the O–C curve of FG Hya can be explained as a combination of a secular period decrease and a cyclic variation with a period of 36.4 yr and an amplitude of 0.0289 d. By comparing the variation of the depth of the primary minimum with the change of the cyclic period, it is discovered that both of them may vary with the same cycle length of 36.4 yr and in the same phase. The variation of the light curve, the spotted primary component and the connection between the cyclic period change and the depth of the primary minimum, all may suggest that the G0-type component displays solar-type magnetic activity with a 36.4-yr cycle length. The long-time period decrease is interpreted by mass transfer from the more massive component to the less massive one or/and angular momentum loss due to mass outflow from the outer Lagrangian point. 相似文献
10.
B. Paczy&#;ski D. M. Szczygie&#; B. Pilecki G. Pojma&#;ski 《Monthly notices of the Royal Astronomical Society》2006,368(3):1311-1318
The All Sky Automated Survey (ASAS) is a long-term project to monitor bright variable stars over the whole sky. It has discovered 50 099 variables brighter than V < 14 mag south of declination +28°, and among them 11 076 eclipsing binaries. We present a preliminary analysis of 5384 contact, 2949 semi-detached, and 2743 detached systems. The statistics of the distribution provides a qualitative confirmation of decades old idea of Flannery and Lucy that the W UMa-type binaries evolve through a series of relaxation oscillations: the ASAS finds comparable number of contact and semi-detached systems.
The most surprising result is a very small number of detached eclipsing binaries with periods P < 1 d , the systems believed to be the progenitors of the W UMa stars. As many (perhaps all) contact binaries have companions, there is a possibility that some were formed in a Kozai cycle, as suggested by Eggleton and his associates. 相似文献
The most surprising result is a very small number of detached eclipsing binaries with periods P < 1 d , the systems believed to be the progenitors of the W UMa stars. As many (perhaps all) contact binaries have companions, there is a possibility that some were formed in a Kozai cycle, as suggested by Eggleton and his associates. 相似文献
11.
R. W. Hilditch 《Astrophysics and Space Science》2006,304(1-4):203-206
A review is presented of the progress that has been made in the last 3 years towards quantifying the properties of high-mass detached and semi-detached eclipsing binaries in Local Group galaxies. Comparisons between these observational results on masses, radii, temperatures and luminosities for stars in detached binaries and evolution models for single stars at the appropriate metallicity are found to be very good. New evolution models for interacting binaries passing through case A mass exchange are being calculated, and indicate a requirement for some mass loss to find agreement with the observational data. The observational data on such semi-detached systems show similar properties to those in the Milky Way galaxy. The directly-determined distances to all these eclipsing binaries are proving to be most valuable for strengthening the distance scale amongst the Local Group galaxies. 相似文献
12.
Enikö Regös Vernon C. Bailey Rosemary Mardling 《Monthly notices of the Royal Astronomical Society》2005,358(2):544-550
The concept of Roche lobe overflow is fundamental to the theory of interacting binaries. Based on potential theory, it is dependent on all the relevant material corotating in a single frame of reference. Therefore if the mass losing star is asynchronous with the orbital motion or the orbit is eccentric, the simple theory no longer applies and no exact analytical treatment has been found. We use an analytic approximation whose predictions are largely justified by smoothed particle hydrodynamic simulations (SPH). We present SPH simulations of binary systems with the same semi-major axis a = 5.55 R⊙ , masses M 1 = 1 M⊙ , M 2 = 2 M⊙ and radius R 1 = 0.89 R⊙ for the primary star but with different eccentricities e = 0.4, 0.5, 0.6 and 0.7. In each case the secondary star is treated as a point mass. When e = 0.4 no mass is lost from the primary while at e = 0.7 catastrophic mass transfer, partly through the L2 point, takes place near periastron. This would probably lead to common-envelope evolution if star 1 were a giant or to coalescence for a main-sequence star. In between, at e ≥ 0.5 , some mass is lost through the L1 point from the primary close to periastron. However, rather than being all accreted by the secondary, some of the stream appears to leave the system. Our results indicate that the radius of the Roche lobe is similar to circular binaries when calculated for the separation and angular velocity at periastron. Part of the mass loss occurs through the L2 point. 相似文献
13.
Melvyn B. Davies rew King Hans Ritter 《Monthly notices of the Royal Astronomical Society》2002,333(2):463-468
We investigate whether the recently observed population of high-velocity white dwarfs can be derived from a population of binaries residing initially within the thin disc of the Galaxy. In particular, we consider binaries where the primary is sufficiently massive to explode as a Type II supernova. A large fraction of such binaries are broken up when the primary then explodes as a supernova, owing to the combined effects of the mass loss from the primary and the kick received by the neutron star on its formation. For binaries where the primary evolves to fill its Roche lobe, mass transfer from the primary leads to the onset of a common envelope phase during which the secondary and the core of the primary spiral together as the envelope is ejected. Such binaries are the progenitors of X-ray binaries if they are not broken up when the primary explodes. For those systems that are broken up, a large number of the secondaries receive kick velocities ∼100–200 km s−1 and subsequently evolve into white dwarfs. We compute trajectories within the Galactic potential for this population of stars and relate the birth rate of these stars over the entire Galaxy to those seen locally with high velocities relative to the local standard of rest (LSR) . We show that for a reasonable set of assumptions concerning the Galactic supernova rate and the binary population, our model produces a local number density of high-velocity white dwarfs compatible with that inferred from observations. We therefore propose that a population of white dwarfs originating in the thin disc may make a significant contribution to the observed population of high-velocity white dwarfs. 相似文献
14.
H. Ritter 《Monthly notices of the Royal Astronomical Society》1999,309(2):360-372
We derive a simple analytical solution for the evolution of a close binary with nuclear time-scale driven mass transfer from a giant. This solution is based on the well-known fact that the luminosity and the radius of a giant scale to a good approximation as simple power laws of the mass M c of the degenerate helium core. Comparison with results of numerical calculations by Webbink, Rappaport & Savonije show the analytical solution and the power-law approximation to be quite accurate. The analytical solution presented does also allow (in parametrized form) for non-conservative mass transfer. Furthermore, it is shown that the near constancy of the mass-transfer rate over most of the mass-transfer phase seen in the results by Webbink, Rappaport & Savonije is not a generic feature of this type of evolution but rather a consequence of a particular choice of parameters. The analytical solution also demonstrates that the level of mass transfer is largely set by the core mass of the giant at the onset of mass transfer. Finally, we show that the model is self-consistent and discuss its applicability to low-mass X-ray binaries. 相似文献
15.
Traditionally, some physical details(e.g., magnetic braking, energy transfer, angular momentum loss, etc.) have to be taken into consideration during investigations into the evolution of contact binaries. However, the real evolutionary processes which usually contain several of these physical mechanisms are very complicated as a result of strong interaction between components. To avoid dealing with these factors, a linear relationship is applied to the temperatures of components. It is found that the higher the mass ratio(M_2/M_1) of a contact system, the weaker the deviation from thermal equilibrium.On this basis, a variation trend of fill-out factor(f) changing with mass ratio can be inferred, which is consistent with observations. Moreover, if we stick to this point of view, it should be natural that the number of semi-detached binaries in the predicted broken-contact phase of relaxation oscillations is less than the number in the contact phase. 相似文献
16.
Pritchard Tobin Clark & Guinan 《Monthly notices of the Royal Astronomical Society》1998,297(1):278-290
Using improved techniques, high-quality CCD uvbyVI C photometry has been obtained for the 14th magnitude eclipsing binaries HV 1620 in the Small Magellanic Cloud (SMC) and HV 2241 in the Large Magellanic Cloud (LMC). IUE ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson & Devinney synthetic light-curve code and Kurucz model atmospheres. Both systems are semi-detached and appear to have undergone mass exchange. In HV 1620 the mass ratio and the effective temperatures of the primary and secondary are q = M 2 / M 1 = 0.68 ± 0.03, T eff,1 = 33 000 ± 4500 K and T eff,2 = 24 000 ± 3500 K. The corresponding values for HV 2241 are 0.53 ± 0.01, 27 000 ± 3000 K and 20 200 ± 1500 K. Using the radial-velocity curves obtained by Niemela & Bassino with a 1-m telescope, we find that both systems are massive, as expected. Reddening considerations suggest both systems may lie towards the rear of their respective Clouds. 相似文献
17.
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.... 相似文献
18.
K. Stpie&#; 《Monthly notices of the Royal Astronomical Society》2009,397(2):857-867
A hydrodynamic model for the energy transport between the components of a contact binary is presented. Energy is transported by a large-scale, steady circulation carrying high entropy matter from the primary to secondary component. The circulation is driven by the baroclinic structure of the common envelope, which is a direct consequence of the non-uniform heating at the inner critical Roche lobes due to unequal emergent energy fluxes of the components. The mass stream flowing around the secondary is bound to the equatorial region by the Coriolis force and its width is determined primarily by the flow velocity. Its bottom is separated from the underlying secondary's convection zone by a radiative transition layer acting as an insulator. For a typically observed degree of contact the heat capacity of the stream matter is much larger than radiative losses during its flow around the secondary. As a result, its effective temperature and entropy decrease very little before it returns to the primary. The existence of the stream changes insignificantly specific entropies of both convective envelopes and sizes of the components. Substantial oversize of the secondaries, required by the Roche geometry, cannot be explained in this way. The situation can, however, be explained by assuming that the primary is a main-sequence star whereas the secondary is in an advanced evolutionary stage with hydrogen depleted in its core. Such a configuration is reached past mass transfer with mass ratio reversal. Good agreement with observations is demonstrated by model calculations applied to actual W UMa-type binaries. In particular, a presence of the equatorial bulge moving with a relative velocity of 10–30 km s−! around both components of AW UMa is accounted for. 相似文献
19.
Lifang Li Zhanwen Han Fenghui Zhang 《Monthly notices of the Royal Astronomical Society》2005,360(1):272-281
In a previous paper, using Eggleton's stellar evolution code, we have discussed the structure and evolution of low-mass W Ursae Majoris (W UMa) type contact binaries with angular momentum loss owing to gravitational radiation or magnetic braking. We find that gravitational radiation is almost insignificant for cyclic evolution of low-mass W UMa type systems, and it is possible for angular momentum to be lost from W UMa systems in a magnetic stellar wind. The weaker magnetic activity shown by observations in W UMa systems is likely caused by the lower mass of the convective envelopes in these systems than in similar but non-contact binaries. The spin angular momentum cannot be neglected at any time for W UMa type systems, especially for those with extreme mass ratios. The spin angular momenta of both components are included in this paper and they are found to have a significant influence on the cyclic evolution of W UMa systems. We investigate the influence of the energy transfer on the common convective envelopes of both components in detail. We find that the mass of the convective envelope of the primary in contact evolution is slightly more than that in poor thermal contact evolution, and that the mass of the convective envelope of the secondary in contact evolution is much less than that in poor thermal contact evolution. Meanwhile, the rate of angular momentum loss of W UMa type systems is much lower than that of poor thermal contact systems. This is indeed caused by the lower masses of the convective envelopes of the components in W UMa type systems. Although the models with angular momentum loss for W UMa systems exhibit cyclic evolution, they seem to show that a W UMa system cannot continue this type of cyclic evolution indefinitely, and it might coalesce into a fast-rotating star after about 1200 cycles of evolution (about 7.0 × 109 yr ). 相似文献
20.
Qian Shengbang 《Astrophysics and Space Science》2000,274(4):711-718
The photoelectric observations of the neglected binary AV Hya published by Srivastava and Kandpal (1980) have been re-analyzed using Wilson-Devinney's synthetic light-curve program. The binary turns out to be a near-contact semi-detached system. The primary, more massive, more luminous and greater component, eclipsed at primary minimum, is detached from its Roche lobe (85%). The secondary fills its Roche lobe and has a temperature difference of T=,-3414 K. As with other semi-detached binaries, the secondary is more evolved than that of the primary. Thetimes of light minima of the eclipsing have been analyzed,showing that the orbital period of AV Hya undergoes acontinuous decrease with a rate of dP/dE=-8.26×10-8 day/year. The mass transfer between the twocomponents can not explain the present orbital period variationsince the secondary component is filling the Roche lobe. Theorbital period change demonstrates that the system may undergoa secular mass and angular momentum loss and the system mayevolve from the present short-period near-contact system intoan A-type contact binary. 相似文献