Case a evolution of massive close binary systems

The evolution of three close binary systems of total mass 20.4M in and after the phase of mode Br mass-transfer in caseA of mass exchange is investigated. In every case a secondary component evolves to interfere with the progress of primary's evolution and the system overflows the outer critical surface before the primary completes its nuclear-burning evolution. This strongly indicates the importance of simultaneous calculation of both components. A summary of evolution of the systems considered in this series of papers up to the stage ofL ₂-overflow is given. The observational aspects of the numerical models are also discussed.     

A long-enduring multi-source burst at 17 GHz and its relation to a type IVm-dm burst with spectral fine features

A proton-event-associated microwave burst occurred on November 10, 1978 and was observed with the 17 GHz interferometer at Nobeyama. The burst had a very broad extent of about 4.5 arc and consisted of at least four separate sources. The time evolutions of the individual sources were almost independent of each other. We suggest that the sources are fallen into two distinct types as follows: (i) The two-ribbon-associated sources are characterized by the source expansion in size and the relatively flat microwave spectrum, both of which can be explained by thermal emission from hot condensed plasma in the magnetic arcades whose legs are seen as the two-ribbon H flare, and (ii) the spot-related sources are characterized by the high polarization degree with a compact unipolar structure, the rapid time variation, and the inverted-U shape microwave spectrum. The intimate relation of the latter sources to the evolution of the associated type IV_m-dm burst with spectral fine features is also discussed.     

Evolution of close binaries and origin of Algol-type systems

The evolution of close binary systems was followed for ten systems with the initial mass of the primary in the range 1–4M and with different initial mass ratios and initial separations. A brief discussion of the evolution of the contact component is presented for two separate cases: when the primary reaches its Roche lobe during central hydrogen burning (case A) and after the exhaustion of hydrogen in the center (case B).The models obtained are compared with observed semi-detached systems separately for massive (with total mass greater than 5M ) and low mass (with total mass below 4M ) binaries. It is shown that the contact components of the observed massive binaries are probably burning hydrogen in the core. On the contrary, the majority of contact components of the observed low-mass binaries are burning hydrogen in the shell. The observed distribution of such binaries as a function of different luminosity excesses of contact components seems to indicate that their origin is connected with case A rather than with case B.     

The chemical composition of matter in the early universe

The results of the computations of the chemical evolution for a galaxy cluster are presented. The matter exchange between galaxies and intergalactic medium is taken into account. Two dependences of star formation rate on time are considered: (i) monotonously decreasing dependence characteristic of elliptical galaxies, (ii) dependence having two peaks associated with creation of spiral galaxy subsystems, with suppression of star formation at the period between maxima. It is assumed that galactic ejection is due to explosions of II-type supernova with massesm5M , and that the accretion on to a galaxy depends but weakly on the time. By comparing the obtained results with total combination of available observations, it is established that the rate of gaseous exchange between a galaxy and intergalactic medium should be rather large: 0.03M _gal Gyr^–1. Besides, the activity of each type of galaxy leads to an approximately equal enrichment of intergalactic gas by new elements synthesized in the stars. The existence of a large accretion on to the Galaxy leads to the decrease of primordial deuterium abundance by a factor of no more than 2 during the galaxy evolution time. It enables us to assume that the standard Big Bang model with baryon density parameter _b 0.1 may be considered as true.     

Microstructures in type III events in the solar wind

A model is presented for the generation and evolution of bump-in-tail driven Langmuir waves in the solar wind during type III emission, which removes a number of apparent inconsistencies between theory and observations. It is argued that there must be localized enhancements of f _b /v by a factor of 10² over the measured average values. Growth rates and energy densities of Langmuir waves are, therefore, considerably enhanced, permitting growth to overcome linear scattering losses, and also allowing nonlinear decay into ion-acoustic waves, in line with observations. Estimates are made of the probability distribution p(E), of wave field strengths E, based on linear and nonlinear wave-packet evolution, yielding p(E) E ^–a, 3. This helps explain why very high values of E are rarely found in the measured spiky wave turbulence.     

Late stages of the evolution of close binaries

Close binaries can evolve through various ways of interaction into compact objects (white dwarfs, neutron stars, black holes). Massive binary systems (mass of the primaryM ₁ larger than 14 to 15M ₀) are expected to leave, after the first stage of mass transfer a compact component orbiting a massive star. These systems evolve during subsequent stages into massive X-ray binaries. Systems with initial large periode evolve into Be X-ray binaries.Low mass X-ray sources are probably descendants of lower mass stars, and various channels for their production are indicated. The evolution of massive close binaries is examined in detail and different X-ray stages are discussed. It is argued that a first X-ray stage is followed by a reverse extensive mass transfer, leading to systems like SS 433, Cir X1. During further evolution these systems would become Wolf-Rayet runaways. Due to spiral in these system would then further evolve into ultra short X-ray binaries like Cyg X-3.Finally the explosion of the secondary will in most cases disrupt the system. In an exceptional case the system remains bound, leading to binary pulsars like PSR 1913+16. In such systems the orbit will shrink due to gravitational radiation and finally the two neutron stars will coalesce. It is argued that the millisecond pulsar PSR 1937+214 could be formed in this way.A complete scheme starting from two massive ZAMS stars, ending with a millisecond pulsar is presented.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia 3–7 June, 1983.     

The luminosity-dependent evolution function of flat-spectrum radio sources at 5 GHz

The numerical method for obtaining the luminosity-dependent evolution function of radio sources is presented and applied to the flat spectrum radio sources selected at 5 GHz.The method constructed on the basis of the iterative one given by Robertson, which requires assuming a specific type of the searched function enables one to obtain the evolution function of sources with radio flux densityS _5.01 mJy.The influence of the shape of the local RLF, of the luminosity distributionN(P) and of the spectral index function on the resulting evolution function is investigated. The results presented show that the luminosity dependence of the evolution function of flat-spectrum radio sources is significant and should not be neglected. The obtained evolution function, which allows one to reproduce the source counts curve, the redshift distribution, and the spectral index distribution, may exhibit the redshift cut-off at z₀3.     

Dynamical effects of dark matter in systems of galaxies

SeveralN-body experiments were performed in order to simulate the dynamical behaviour of systems of galaxies gravitationally dominated by a massive dark background.We discuss mass estimates from the dynamics of the luminous component (M _VT) under the influence of such a background, assuming a constant dark/luminous mass ratio (M _D/M _L) and plausible physical conditions. We extend in this way previous studies (Smith, 1980, 1984) about the dependence ofM _VT on the relative distributions of dark and luminous matter (Limber, 1959). We found that the observed ratio of the virial theorem mass to luminosity (M _VT/L) in systems of galaxies of different sizes could be the result of different stages of their post-virialisation evolution as was previously suggested by White and Rees (1978) and Barnes (1983). This evolution is mainly the result of the dynamical friction that dark matter exerts on the luminous component. Thus our results give support to the idea that compact groups of galaxies are dynamically more evolved than large clusters, which is expected from the hierarchical clustering picture for the formation of such structures.     

Singular points of the polarization tensor

The problem to compute the magnetic field above the chromosphere using data of the vector = B _t/Bt that gives the projected field direction can be solved with different approximations. The field of direction vectors is, however, not the only field accessible to observations. The Stokes parameters, which are components of the radiation tensor, can be measured at each point of the image plane. The directions of the eigenvectors of the radiation tensor define two mutually orthogonal systems of integral curves in the image plane. These families of curves have singular points, which are generally of different type than those of the vector field. When the morphology of H chromospheric fibrils are used to infer the topology of the magnetic field, a similar problem is met, suggesting that singular points should also be present there.     

The angular momentum loss of low-mass close binary systems

The detailed evolution of low-mass main-sequence stars (M < 1M ) with a compact companion is studied. For angular momentum loss associated with magnetic braking it is found that about 10^–11–10^–12 M yr^–1 in stellar wind loss would be required. This wind is 10²–10³ times stronger than the solar wind, so we believe here magnetic stellar wind is insufficient. It is well known that there is mass outflow in low-mass close binary systems. We believe here that these outflows are centrifugal driven winds from the outer parts of the accretion disks. The winds extract angular momentum from these systems and therefore drive secular evolution. Disk winds are preferred to winds from the secondary, because of the lower disk surface gravity.     

Chemical evolution of two-component galaxies

In this paper, we try to insert into a single evolutionary scheme — in dealing with chemical evolution of galaxies — two different viewpoints that (at least in not too much complicated models) have been treated separately: namely, theS models, allowing mass conservation; andI models, allowing initial zero masses and no mass conservation due to gas inflow. The true evolution of a real proto-galaxy (after reaching the state of maximum expansion) is simulated as follows: A spheroidal gas mass continued to collapse and form stars until a flat configuration is reached after a timeT _c has elapsed, while a given amount of gas flows in on a time-scale . According to this scheme, the basic equations of chemical evolution are derived and models which simulate the history of solar neighborhood, other regions and Galactic spheroid component are built up, in the whole range between theS-limit (mass conservation) and theI-limit (zero initial mass and subsequent accretion due to inflowing gas). Concerning the solar neighbourhood, we find that neither the occurrence of gas inflow nor inflow on time-scales 2–3 10⁹ yr are necessary in order to reproduce the temporal behaviour and the empirical distribution of metal content, as pointed out by some authors. On the contrary, the constraint on the lower mass limit for stars formed,m _mf0.01, allows only models with T _c (i.e. inflow time-scale of the order of the contraction time), while the constraint on the disk mass fraction,R _D(T _a)0.75, rules out the cases near theI-limit forT _c0.55 but permits all cases forT _c2.75. Concerning other regions, models are built up which roughly simulate elliptical, spiral and irregular galaxies, and all less extended regions resembling such systems.If the stellar birthrate function is assumed to be an universal law, the chemical evolution of the Galactic disk may be understood in terms of different zones (that might be thought as concentric and coaxial rings) the total density of which decreases monotonically, owing to a corresponding decrease in total mass and/or increase in volume, when passing from the center to the border of the disk. The constraintsm _mf0.01 andR _D(T _a)0.75 for different regions of the Galactic disk would also rule out all models well beyond theS-limit, but further results are required in order to confirm this conclusion. Finally, concerning the Galactic spheroid component, it is found that onlyS models with massive halos (R _D(T _a)0.01) are able to reproduce in an acceptable way the empirical metal abundance distribution. In order to obtain a complete fit, a spheroid component has to be assumed, with a steeper mass spectrum exponent in the stellar birthrate function, and a lower yield of metallicity, in respect to the disk component. According to this last model, a mean value of disk metal content (with respect to spatial distribution) of the order of the solar value also results.     

Interpretation of distinct type IVmA- and IVμ-bursts on the basis of micro-instabilities and of resonant nonlinear interaction of waves

The generation of space charge waves by micro instabilities of the Harris type and their conversion into electromagnetic waves is discussed in the framework of the dispersion curves of the extraordinary wave mode in the warm plasma. Acceleration of electrons as also nonlinear interactions of waves are taken into account. A survey of the parameter regions of the Harris instabilities is given. Distinct values _p / _c and _p / _c result, enabling the instability as well as the conversion. The moving type IVmA bursts, and on the other side the impulsive cm-bursts and the first phase of type IV bursts are correlated to different values _p / _c and corresponding heights in the corona. The space charge waves can produce hydromagnetic waves by parametric excitation, too (type II bursts). The proposed mechanism is discussed with respect to the energy balance and to the magnetic configurations derived from observations with the Culgoora radioheliograph.     

On the evolution of a system of intergalactic clouds

The presence of L _a -forests in the spectra of quasars is considered as proof of the fragmentary structure of the intergalactic medium. The masses of the clumps (of clouds) will increase as they merge together. Once the radial concentration of neutral hydrogen in a cloud attains its critical value, star formation begins, and the cloud turns into a galaxy. Certain physical properties of clouds are considered and a new approach to the investigation of the evolution of systems of clouds is proposed.Translated from Astrofizika, Vol. 37, No. 1, pp. 35–42, January–March, 1994.     

On the evolution of low mas binary systems

The evolution of parameters of close binary systems containing a red dwarf (with mass loss) and a condensed star is investigated. The mass loss from the system and asynchronism of the red dwarf rotation are taken into consideration. The calculations show that if the initial mass ratioq ₀2 then during 10⁷ yr the instability of mass loss process arises, and a bright X-ray source forms with luminosity close to the Eddington one. Ifq ₀>2 then during the mass loss phase the bright X-ray source arises twice. The models explain the existence of the forbidden interval of orbital periods and the absence of systems with periods less than 80 min.     

Distribution of minima of the current size of the triple systems and their disruption

The dynamical evolution of triple systems has been studied by computer simulations. A function (t) has been defined, where p is the maximum distance of the components from their centre of inertia, and t is the time. The value of is used to indicate the current size of the triple system. The minima of have been followed during the course of evolution of the triples. A distribution of f(_min) has been obtained, which is described by the following statistical parameters: the mode is equal to 0.65d, the mean value _min= 0.750d, r.m.s. is 0.477d, the asymmetry is 0.218, the excess is 2.04 where d is the mean harmonic distance between the bodies in the equilibrium state of the triple system. As a rule, escapes from triples occur only after close three-body approaches.     

Dynamical conditions in planets and stars

With the available data in planets, stars and galaxies, it is studied the functions of angular momentaJ(M) and amounts of actionA _c(M) (associated to the non rotational terms in the kinetic energy). The results indicate that independently of how are these functionsJ(M),A _c(M) their ratioA _c/J remains a near invariant. It is independent also from the type of angular momenta: intrinsic spins of the bodies or the total angular (orbital) momenta of the bodies forming a system; for instance, the Solar System and the planets.The relationA _c(M) for the Solar System are analogous to these in the FGK stars of the main sequence, and the relationJ(M) (also for the Solar System) is analogous to the lower possible limit for binary stars.The different types of binary stars from the short period, detached systems to contactary systems, gives a range of functionsJ(M),A _c(M) that are the same that one can expect in stars with planetary systems. According to the detection limits given for planetary companions by Campbell, Walker and Yang (1988) (masses of less than 9 Jupiter masses and orbital periods of less than 50 years) we calculate the limits forJ(M) andA _c(M) This gives a lower limitA _c/J 1 associated to stars with planetary systems as 61 Cygni and to short period detached binaries. The upper limitA _c/J 16 correspond to planetary systems as the ours and probably to cataclysmic binaries. There are reasons to suspect that systems as the ours and in range 4 A _c/J 16 (with a lower limit analogous to contactary binaries as Algols and W Ursa Majoris) must be the most common type of planetary systems. The analogies with the functionsJ(M)A _c(M) for galaxies suggest cosmogonical conditions in the stellar formation.Independently of this, one can have boundary conditions for the Jacobi problem when applied to a collapsing cloud. Namely, from the initial stage (a molecular cloud) to the final stage (a formed stellar system: binary or planetary) the angular momenta and amounts of action decayed to 10^~4 the initial values, but in such a form thatA _c(t)/J(t) remains a near invariant.     

Close binary systems before and after mass transfer: A comparison of observations and theory

From a search through the literature 174 close binaries with known absolute dimensions have been sampled. Distinction is made between systems before and after mass exchange. Mass, period and mass ratio distributions and relations of the group of unevolved binaries (i.e., prior to mass exchange) are transformed into corresponding distributions and relations of evolved binaries. The transformations are based upon theM _1f=g(M _1f) relation derived from an extended set of published theoretical computations of the evolution of close binaries. From this relation the following characteristics of the system after mass exchange are computed:M _1f,M _2f (andq _f),P _f. Five different modes of mass transfer were applied for the computation of the values ofP _f andM _2f. The variation of the period was calculated using the formalism given by Vanbeverenet al. (1979). The results are compared to the observations of binary systems after mass exchange, and are discussed together with an analysis of the effect of several selection effects present in the distributions. The main conclusion is that, during mass exchange in close binaries, more than 50% of the mass is lost to the system in the process of transfer, removing a large amount of angular momentum.This research is supported by the National Foundation of Collective Fundamental Research of Belgium (F.K.F.O.) under No. 2.9009.79.     

Co-Orbital Motion with Slowly Varying Parameters

We consider the dynamics of a test particle co-orbital with a satellite of mass m _s which revolves around a planet of mass M ₀ m _s with a mean motion n _s and semi-major axis a _s. We study the long term evolution of the particle motion under slow variations of (1) the mass of the primary, M ₀, (2) the mass of the satellite, m _s and (3) the specific angular momentum of the satellite J _s. The particle is not restricted to small harmonic oscillations near L ₄ or L ₅, and may have any libration amplitude on tadpole or horseshoe orbits. In a first step, no torque is applied to the particle, so that its motion is described by a Hamiltonian with slowly varying parameters. We show that the torque applied to the satellite, as measured by _s = j_s/(n _s J _s) induces an distortion of the phase space which is entirely described by an asymmetry coefficient = _s/, where = m _s/M. The adiabatic invariance of action implies furthermore that the long term evolution of the particle co-orbital motion depends only on the variation of m _s a _s with time. Applying a constant torque to the particle, as measured by _s = j_s/(n _s J _p) is then merely equivalent to replacing = _s/ by = (_s – _p)/. However, if the torque acting on the particle exhibits a radial gradient, then the action is no more conserved and the evolution of the particle orbit is no more controlled by m _s a _s only. We show that even mild torque gradients can dominate the orbital evolution of the particle, and eventually decide whether the latter will be pulled towards the stable equilibrium points L ₄ or L ₅, or driven away from them. Finally, we show that when the co-orbital bodies are two satellites with comparable masses m ₁ and m ₂, we can reduce the problem to that of a test particle co-orbital with a satellite of mass m ₁ + m ₂. This new problem has then parameters varying at rates which are combinations, with appropriate coefficients, of the changes suffered by each satellite.     

The mass-ratio distribution of spectroscopic binary stars

In order to determine the mass-ratio distribution of spectroscopic binary stars, the selection effects that govern the observations of this class of binary systems are investigated. The selection effects are modelled numerically and analytically. The results of the models are compared to the data inThe Eighth Catalogue of the Orbital Elements of Spectroscopic Binary Stars (DAO8) compiled by Battenet al. (1989). The investigations involve binary systems with Main-Sequence primary components only, in order to avoid confusion of evolutionary and selection effects.For single-lined spectroscopic binaries (SBI) it is found that the mass ratios (q=M _sec/M _prim) in general adhere to a distribution _q q ^-2 forq>q ₀, withq ₀=0.3. The observations are consistent with a distribution that is flat forq<q ₀. The turn-over value varies fromq ₀=0.3 for systems with B-type primaries, toq ₀=0.55 for systems with K-type primaries. The semi-major axesa ₁ are distributed according to _a (a ₁)a ₁ ^-a with an average value of _a =1.3. The power varies from _a =1.7 for systems with B-type primaries to _a =0 for systems with K-type primaries. The eccentricitiese of the orbits of SBI systems are distributed according to _e (e)e ^-1.For double-lined spectroscopic binary stars (SBII) it is found that the shape of theq-distribution, as derived from observations, is almost entirely determined by selection effects. It is shown that the distribution is compatible with theq-distribution found for SBI systems. A sub-sample, consisting of the SBII systems from DAO8 with magnitudesm _V 5 ^m , is less hampered by selection effects, and shows the same shape of theq-distribution as the SBI systems, at theq-interval (0.67, 1).It is estimated that 19–45% of the stars in the solar neighbourhood are spectroscopic binary systems.     

Semi-detached binaries: The origin and present status of TU Mon,SX Cas,and DM Per

An attempt is made to trace back the possible progenitor systems of the Algol-type binaries TU Mon, SX Cas, and DM Per. The present characteristics are compared to the result of the evolution of 9M ₀+5.4M ₀. The position of the hot components in the HRD is discussed with regard to the theoretical models.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia 3–7 June, 1983.