Evolution Of Close Binary Systems Research Articles

Next to leading-order gravitational wave emission and the dynamical evolution of close binary systems with spin

Close binary systems with spinning components are considered. Finite size effects due to rotational deformation are taken into account. The dynamical evolution and next to leading-order gravitational wave forms are calculated, taking into account the orbital motion up to the first post-Newtonian approximation. The analysis presented here will be relevant mainly for white dwarf binaries and, to some extent, also to compact binaries with a fast spinning neutron star component.

Direct diameter measurement of a star filling its Roche lobe

Context.Stellar evolution in close binary systems is strongly influenced by mass transfer from one star to the other when one component fills its zero-velocity surface or Roche Lobe. SS Lep is a fairly nearby close binary showing the Algol paradox and a shell spectrum, both indicative of (past) mass transfer.

Highly evolved close binary systems

The basic properties of highly evolved close binary systems are described. In these systems the first mass exchange between the components is completed and peculiar objects are formed: Wolf–Rayet stars, white dwarfs, neutron stars and black holes. The observational characteristics of these systems are in agreement with the modern theory of evolution of close binary systems. Investigation of these systems is very important for astrophysics and fundamental physics. In particular, 20 black-hole candidates of stellar masses have been discovered up to now in highly evolved close binaries. A catalogue of highly evolved close binary stars is described as well as its new electronic version, work on which is in progress at the Sternberg Astronomical Institute.

Angular momentum evolution of Algol binaries

We have compiled the well-determined absolute parameters of Algol-type binaries. The lists contain the parameters of 74 detached and 61 semidetached close binaries. The double-lined eclipsing binaries provide not only the most accurate determinations of stellar mass, radius and temperatures but also distance-independent luminosity for each of their individual components. The distributions of the primary and secondary masses of detached binaries (DBs) are similar, whilst the secondary masses of the semidetached binaries (SDBs) are mostly smaller than 2 M ⊙ with a peak in the M 2 -bin (0.21-1.0). The components of the DBs are almost all located ' in the main-sequence band. On the contrary, the secondary components of the SDBs have larger radii and luminosity with respect to the same mass and the same effective temperature of main-sequence counterparts. They occupy a region of the Hertzsprung-Russell diagram between terminal-age main sequence and giants. Moreover, the total angular momenta and specific angular momenta are larger for the SDBs of orbital periods with P > 5 d than those of the shorter period ones. The specific angular momenta of SDBs with periods longer than 5 d are 65 per cent greater than that of the short period group with the same mass. The DBs and the SDBs with orbital periods longer and shorter than 5 d are separated into three groups in the J/M 5/3 - q diagram. The SDBs with mass ratios greater than 0.3 and P > 5 d have almost the same angular momentum to those of DBs. However, the SDBs with short periods have the smallest angular momentum even though they have the same mass ratios. This result reveals that angular momentum loss (AML) considerably affects the evolution of close binary systems. Recently, Chen, Li & Qian suggested that, in addition to magnetic braking, a circumbinary disc may play an important role in AML from Algol-type binaries. Their calculations indicated that the evolution of Algol-type binaries can be significantly affected by the circumbinary disc. Our results show that the evolution of close binaries begins as a DB and losing angular momentum, first via stellar wind and then magnetic braking plus circumbinary disc the period is shortened and orbit shrinks. Thereafter, the evolution of the system is accelerated and mass transfer rates are enhanced which result in a smaller mass ratios.

Evolution of Close Binary Systems

We collected data on the masses, radii, etc. of three classes of close binary stars: low-temperature contact binaries (LTCBs), near-contact binaries (NCBs), and detached close binaries (DCBs). They restrict themselves to systems where (1) both components are, at least arguably, near the Main Sequence, (2) the periods are less than a day, and (3) there is both spectroscopic and photometric analysis leading to reasonably reliable data. They discuss the possible evolutionary connections between these three classes, emphasizing the roles played by mass loss and angular momentum loss in rapidly-rotating cool stars.

Getting Its Kicks: A VLBA Parallax for the Hyperfast Pulsar B1508+55

The highest velocity neutron stars establish stringent constraints on natal kicks, asymmetries in supernova core collapse, and the evolution of close binary systems. Here we present the first results of a long-term pulsar astrometry program using the VLBA. We measure a proper motion and parallax for the pulsar B1508+55, leading to model-independent estimates of its distance (2.37+0.23-0.20 kpc) and transverse velocity (1083+103-90 km/s), the highest velocity directly measured for a neutron star. We trace the pulsar back from its present Galactic latitude of 52.3 degrees to a birth site in the Galactic plane near the Cyg OB associations, and find that it will inevitably escape the Galaxy. Binary disruption alone is insufficient to impart the required birth velocity, and a natal kick is indicated. A composite scenario including a large kick along with binary disruption can plausibly account for the high velocity.

The evolution of close binary systems with intermediate-mass black holes and ultra-luminous X-ray sources

The results of numerical studies of the evolution of a close binary system containing a black hole with a mass of ∼3000M ⊙ are presented. Such a black hole could form in the center of a sufficiently rich and massive globular cluster. The secondary could be a main-sequence star, giant, or degenerate dwarf that fills or nearly fills its Roche lobe. The numerical simulations of the evolution of such a system take into account the magnetic wind of the donor together with the wind induced by X-ray irradiation from the primary, the radiation of gravitational waves by the system, and the nuclear evolution of the donor. Mass transfer between the components is possible when the donor fills its Roche lobe, and also via the black hole’s capture of some material from the induced stellar wind. The computations show that the evolution of systems with solar-mass donors depends only weakly on the mass of the accretor. We conclude that the observed ultra-luminous X-ray sources (L X ≳ 1038 erg/s) in nearby galaxies could include accreting black holes with masses of 102∓104 M ⊙. Three scenarios for the formation of black holes with such masses in the cores of globular clusters are considered: the collapse of superstars with the corresponding masses, the accretion of gas by a black hole with a stellar initial mass (<100M ⊙), and the tidal accumulation of stellar black holes. We conclude that the tidal accumulation of stellar-mass black holes is the main scenario for the formation of intermediate-mass black holes (102∓104 M ⊙) in the cores of globular clusters.

Eclipsing Spectroscopic Binaries in the SMC

The OGLE survey of the SMC has discovered ~1500 eclipsing binaries thereby providing an excellent platform to study the evolution of close binary systems through case A and case B mass-exchange processes. The complementary spectroscopic radial-velocity studies of these binaries are now in progress and are revealing many interesting systems which challenge current theoretical models of close binary star evolution. These studies also provide excellent direct determinations of distances to these binary stars leading to an improved understanding of the mean distance to the SMC and its 3-D structure. Comparisons between these binary-star distances and other methods of determining the mean distance to the SMC will also be made.

A code for stellar binary evolution and its application to the formation of helium white dwarfs

We present a numerical code intended for calculating stellar evolution in close binary systems. In doing so, we consider that mass transfer episodes occur when the stellar size overflows the corresponding Roche lobe. In such situation we equate the radius of the star with the equivalent radius of the Roche lobe. This equation is handled implicitly together with those corresponding to the whole structure of the star. We describe in detail the necessary modifications to the standard Henyey technique for treating the mass loss rate implicitly together with thin outer layers integrations. We have applied this code to the calculation of the formation of low mass, helium white dwarfs in low mass close binary systems. We found that the global numerical convergence properties are fairly good. In particular, the onset and end of mass transfer episodes is computed automatically.

What Can be Done with Small Telescopes?

AbstractModern astronomy has developed rapidly in the last few decades. Large telescopes, several metres in diameter, have been constructed and installed at many sites around the world, in order to carry out high-quality research work at the frontiers of astronomy. In many parts of the world, only small telescopes are available, because of budgetary limitations and the stage of development of science in the country. However, much effort has been put into using these small telescopes to the best of their capabilities. A small telescope with modern detectors can do good astronomical research. Sirindhorn Observatory, Chiang Mai University, is the only observatory in northern Thailand which plays an active role in astronomical research. The major instrument is the 40-cm Cassegrain reflecting telescope with standard wide-band and intermediate band photoelectric photometers, CCD photometers and a CCD spectrograph. Because of Thailand’s hot and humid climate, the telescopes and detectors at Sirindhorn Observatory need regular maintenance. Major research at the Observatory emphasizes the study of physical propoerties and evolution of close binary systems, especially near-contact and contact binaries, by photometric techniques. Networks in this field of research have been established through national and international collaboration with some astronomical institutes in the region. A larger telescope is being developed for more efficiency in operation; it is expected to be able to serve the future development of astronomical research in Thailand.

V392 Orionis: Observations and Evolutionary State of a Low-Mass System

Although the evolution of binary systems has been qualitatively interpreted with the evolutionary scenario, the quantitative interpretation of any observed system is still unsatisfactory due to the difficulty of the quantitative treatment of mass and angular momentum transfer/loss. To reach a true understanding of the evolution of binary systems, we have to accumulate more observational evidence. So far, we have observed several binaries that are short-period and noncontact, and found the existence of extremely small-mass systems. In the present paper, we study another short-period (P=0.659d), noncontact, eclipsing binary system, V392 Ori. We have made photometric and spectroscopic observations of V392 Ori. The light curves are found to vary, suggesting the existence of circumstellar matter around the system. Combining the photometric and spectroscopic results, we obtain parameters describing the system; we find the mass of the primary component is only 0.6Mʘ- undermassive for its spectral and luminosity class A5V, suggesting that a considerable amount of its original mass has been lost from the system during the course of evolution. The low-mass problem is very important for investigation of the evolution of close binary systems: largemass loss within and/or after the main-sequence will have a significant influence on the future evolution of binary systems.

Measurement and study of rotation in close binary stars. V. Orbital circularization : Pan Kai-ke & Tan Hui-song Yunnan Observatory, CAS, Kunming 650011

In this paper, we calculate the characteristic times of orbital circularization for 29 “normal” detached binary systems in Paper (IV), in accordance with Zahn's dynamical and equilibrium tide mechanisms and Tassoul's purely hydrodynamic theory. By comparing the age of each system and its theoretical characteristic time of orbital circularization, we analyze the observed orbital eccentricity of each system and the theoretical predictions on circularization by the above theories. Basically, we find that the predictions by Zahn's mechanisms fit the observations better than those by the hydrodynamic theory, and that dynamical and equilibrium tides seem to be two of the main circularizing mechanisms for close binary systems on the main sequence. However, we also note that some other mechanisms are absolutely necessary in order to fully explain circularization processes in close binaries, especially in understanding the circular orbits of some systems with asynchronous components. We suggest that the purely hydrodynamic theory is probably important during the periods of pre main sequence and post AGB evolution of close binary systems.

Equilibrium, stability, and orbital evolution of close binary systems

We present a new analytic study of the equilibrium and stability properties of close binary systems containing polytropic components. Our method is based on the use of ellipsoidal trial functions in an energy variational principle. We consider both synchronized and nonsynchronized systems, constructing the compressible generalizations of the classical Darwin and Darwin-Riemann configurations. Our method can be applied to a wide variety of binary models where the stellar masses, radii, spins, entropies, and polytropic indices are all allowed to vary over wide ranges and independently for each component. We find that both secular and dynamical instabilities can develop before a Roche limit or contact is reached along a sequence of models with decreasing binary separation. High incompressibility always makes a given binary system more susceptible to these instabilities, but the dependence on the mass ratio is more complicated. As simple applications, we construct models of double degenerate systems and of low-mass main-sequence-star binaries. We also discuss the orbital evolution of close binary systems under the combined influence of fluid viscosity and secular angular momentum losses from processes like gravitational radiation. We show that the existence of global fluid instabilities can have a profound effect on the terminal evolution of coalescing binaries. The validity of our analytic solutions is examined by means of detailed comparisons with the results of recent numerical fluid calculations in three dimensions.

A new technique for calculations of binary stellar evolution, with application to magnetic braking

The authors present a new computational technique for the study of the evolution of close binary systems with collapsed primaries and mass-losing secondaries. In this technique, for the secondary a composite polytrope with indices n = 3 and n = 3/2 is used to represent the structure of the radiative core and convective envelope respectively. All other relevant aspects of the binary stellar evolution are calculated in detail. A wide range of possible magnetic braking laws and an extended portion of the binary evolution is investigated. It is found in particular, that if magnetic braking effects cease or are strongly reduced at the time when the radiative core of the secondary vanishes, then the system should temporarily come out of contact; this effect may be relevant to the 2 - 3 hr "gap" in the orbital period distribution among cataclysmic variables. The authors also consider the potential importance of magnetic braking in driving the high mass transfer rates that are evidently necessary to account for the high X-ray luminosities of the bright galactic-bulge X-ray sources.

International Ultraviolet Explorer observations of the peculiar variable spectrum of the eclipsing binary R Arae

The eclipsing binary system R Arae = HD 149730 is a relatively bright southern system with an orbital period of about 4.4 days. It is a single-lined spectroscopic binary. The spectral class of the primary component is B9 Vp. The system was included in a study of mass flow and evolution in close binary systems using the International Ultraviolet Explorer satellite (IUE). Four spectra in the wavelength range from 1150 to 1900 A were obtained with the far-ultraviolet SWP camera, and six spectra in the range from 1900 to 3200 range were obtained with the mid-ultraviolet LWR camera. The close binary R Arae exhibits very unusual ultraviolet spectra. It appears that no other close binary system, observed with any of the orbiting satellites, shows outside-eclipse ultraviolet continuum flux variations of this nature.

On the Distribution of Young Spectroscopic Binary Stars Over the Major Semiaxes of their Orbits

About 60% of stars of the disc population in our Galaxy are close binary systems (CBS). Half of the known CBS are spectroscopic binary stars (Kraitcheva et al., 1978).To know the distribution of a correlation between the masses of CBS components and semiaxes of their orbits is necessary for the investigation of the origin and evolution of CBS. For such statistical investigations, a catalogue of CBS was compiled at the Astronomical Council. The catalogue is based on the 6th Batten catalogue (Batten, 1967), its extensions (Pedoussant and Ginestet, 1971; Pedoussant and Carquillat, 1973) and data published up to the end of 1980 (Popova et al., 1981). Now it is recorded on magnetic tape and contains data on 1041 spectroscopic binaries; 333 of them are stars with two visible spectra. The latter are mostly systems prior to mass exchange and the distribution of physical parameters in these systems reflects the distribution and presumably conditions at the time of formation. Using some assumptions, we can obtain for spectroscopic binaries masses of the components M1 and M2 (or the ratio q = M1/M2) and semiaxes of their orbits. Masses of components with the known sin i were obtained by the usual technique; when sin i was not known, masses were estimated from the spectra. We shall discuss here the distribution of CBS in the M-a plane.

IUE Ultraviolet Spectra of the Interacting Binary U Cephei

The eclipsing binary U Cephei has proven to be of great interest in the study of stellar evolution in close binary systems. Batten (1974), Hall and Walter (1974), Rhombs and Fix (1976), Markworth (1977), and Olson (1978), among others, have recently reported on their intensive ground based studies of U Cephei. Kondo, McCluskey and Wu (1978) have investigated the ultraviolet light curves of U Cephei obtained with Astronomical Netherlands Satellite (ANS). Kondo, McCluskey and Stencel (1979) have discussed the International Ultraviolet Explorer (IUE) spectra of U Cephei. This paper discusses results incorporating additional IUE high resolution spectra of U Cephei obtained in both far-ultraviolet and mid-ultraviolet spectral regions.

Stellar Evolution and Close Binaries

A general scheme of evolution of close binaries is outlined. Many types of observed systems are classified according to their evolutionary status. Present theory can account reasonably well for the mass transfer between the two components. There is no satisfactory theory of mass and angular momentum loss from binary (as well as single) stars. Most close binaries sooner or later should develop extended common envelopes. A loss of a common envelope may remove a large fraction of mass and most of angular momentum from a binary, and leave as a remnant a very short period and highly evolved system. Binary nuclei of planetary nebulae, cataclysmic variables and some X-ray binaries are produced this way.I shall present here a picture of the evolution of close binary systems (CBS) as it is understood now. This is not intended to be a review, and no attempt has been made to make the list of references complete. Usually I shall refer the first paper on a given subject and/or one of the recent ones, where a large number of other references can be found. There are many reviews and proceedings of various symposia that deal with close binaries. Here are some: Annual Review of Astronomy and Astrophysics (9, 183,14, 119,15, 127,16, 171, 241), IAU Symposia No. 73, 83, 88, IAU Colloquia No. 42, 46, 53. I shall try to emphasize what is known and what is not known, and how various observed systems fit into the theoretical evolutionary scheme. Because of my background I shall give more references to theoretical papers. Nevertheless, I am convinced that it was the theory of close binaries that was guided in its development by the observations, not other way around. In fact the theory predicted very few new phenomena and very few new types of binaries. But it managed to account, at least qualitatively, for the major evolutionary processes, and made it possible to arrange the observed systems into the evolutionary sequences.

HD 50896: an other WR binary star

The current ideas concerning the evolution of close binary systems (van den Heuvel, 1976), accepting the hypothesis that the system is not disrupted by the first supernova (SN) explosion, predict that the Wolf-Rayet phase can occur twice. The first time the companion of the WR star is a normal OB star and the second time it is a collapsed object. In this context, the importance of searching for binary systems with collapsed companions among the “single” WR stars is evident. Due to its large distance from the galactic plane, z = 280 pc (Smith, 1968a), when compared with the average height (z = 60 pc, Cruz-González et al., 1974) of extreme Population I stars, HD 50896 was considered to be a likely candidate to this type of system.

Erratum

In the review of Structure and Evolution of Close Binary Systems, Peter Eggleton, Simon Mitton, and John Whelan, Eds. (29 July 1977), the pagination and price of the book were omitted. They are: xii, 414 pp., illus. Cloth, $39.50; paper, $32.50.