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In this paper we will focus on the crystal engineering of molecular materials exhibiting magnetic and/or electrical properties. The complexity of these materials needs of a precise design of the molecular building blocks, a control of the intermolecular interactions (hydrogen bonds, host/guest interactions, etc.) and a mastery in crystallization techniques in order to design crystal structures exhibiting useful physical properties. We will illustrate this concept through some relevant examples based on two-component hybrid materials. [ABSTRACT FROM AUTHOR]

Game Theory provides suitable tools to share the total utility among the economic agents or players when the possibilities of cooperation enable obtaining the utility of each group or coalition. The semivalues are solution concepts for situations of competence—cooperation that assign to each player a weighted sum of his/her marginal contributions to the coalitions, where the weights only depend on the coalition size. The Shapley value and the Banzhaf value are semivalues. The solutions introduced here are modifications of the semivalues when we consider a priori coalition blocks in the player set. A computation procedure is also offered. [ABSTRACT FROM AUTHOR]

AMAZONAS satellite, launched in the summer of 2004, includes AMERHIS payload, being the first regenerative system using DVB-RCS/DVB-S standards to inter-connect four coverage areas located in Europe and America, in only one single satellite hop. In the frame of SATLIFE, the different regenerative satellite terminals have been enhanced, including standard technologies to optimize performance through the satellite link. Management Station upgrade is in line with these RCST improvements, supporting new video terminals and multicast routing apart from broadcast. Using the new developments in the prototypes, different multimedia services and applications have been integrated over the regenerative satellite network. Index terms: Digital TV, DVB-RCS, IP, Multicast, Multimedia, Network, OBP, Regenerative, Satellite, Video Broadcasting. [ABSTRACT FROM AUTHOR]

The dual-chamber (DC) implantable cardioverter defibrillator (ICD) was primarily introduced in the market to add atrial-based pacing for those patients simultaneously affecting by bradycardia and fatal ventricular arrhythmias. Following the successful introduction of the original VVED ICDs, device capabilities were rapidly expanded by the addition of AV discrimination and atrial anti-tachycardia therapies (DDED ICDs). It was suggested that these sophisticated devices would overcome the limitations of the single chamber (SC) devices and that their recommended use would be extended. [ABSTRACT FROM AUTHOR]

Atrial fibrillation (AF), the most prevalent sustained arrhythmia, is an increasingly common risk factor in patients with severe left ventricular dysfunction. Moreover, it is associated with a poor prognosis and reduced quality of life for patients with heart failure (HF) syndrome. Trials involving HF patients have shown that the prevalence of AF in such patients is high, over 20-40% [1, 2] and increases with progressive NYHA class. AF is a relevant factor in terms of the incidence of stroke, morbidity, refractory arrhythmic episodes, and number of hospitalizations. Moreover, the results of the GUSTO-III trial confirmed that AF is an independent factor for increased mortality after myocardial infarction [3]. A retrospective analysis in the Studies of Left Ventricular Dysfunction Prevention and Treatment Trials showed that patients with AF at baseline, compared to those in sinus rhythm, had significantly greater all-cause mortality (34 vs 23%), death attributed to pump failure (16.7 vs 9.4%), and were more likely to reach the composite end point of death or hospitalization for HF (45 vs 33%). The European GEM DR Evaluation [4] a lso detected a higher early mortality of patients with implanted cardioverter/defibrillators — a population with a high prevalence of HF and left ventricular dysfunction, related to episodes of AF. [ABSTRACT FROM AUTHOR]

The Betic Cordillera, located in the south of the Iberian Peninsula, is currently subjected to NW-SE compression and NE-SW extension. Until a few years ago, there were hardly any geodetic studies to quantify the tectonic deformation taking place in the Betic Cordillera. In 1999, in the framework of an interdisciplinary research project to monitor the deformation, several geodetic studies were initiated by the Universities of Jaén, Granada and Alicante. These studies were centred on the basins of Granada and the Bajo Segura (Alicante), sectors in which the last two destructive earthquakes in the Iberian Peninsula took place. This paper describes the geodynamic context of these study areas and the main features of the geodetic studies, focusing on the deformation analysis of the three observation surveys carried out in 1999, 2000 and 2001 over a non-permanent GPS network established in the Granada Basin. The results agree with the low rates of deformation previously calculated from geological data. To detect such small rates, observation over a longer time span will be needed. [ABSTRACT FROM AUTHOR]

Several new robotic telescopes had or will see first light in 2005/2006 and are designed for either wide-field imaging, high-precision photometry or even for highresolution echelle spectroscopy. These telescopes are in the 1-2 m class and therefore will focus on very specific tasks. Here, I present an update of the robotic STELLA facility currently under construction in Tenerife and emphasize its science capabilities for binary-star research. Among the many science applications of STELLA is the monitoring of magnetic activity in single and binary stars and their relation to age, rotation rate, metallicity and binarity per se. [ABSTRACT FROM AUTHOR]

The Kepler Mission is a photometric space mission that will continuously observe a single 100 square degree field of view (FOV) of the sky of more than 100,000 stars in the Cygnus-Lyra region for four or more years with a precision of 14 parts per million (ppm) for a 6.5 hour integration including shot noise for a twelfth magnitude star. The primary goal of the mission is to detect Earth-size planets in the habitable zone of solar-like stars. In the process, many eclipsing binaries (EB) will also be detected. Prior to launch, the stellar characteristics will have been determined for all the stars in the FOV with K < 14.5. As part of the verification process, stars with transits (about 5%) will need to have follow-up radial velocity observations performed to determine the component masses and thereby separate grazing eclipses caused by stellar companions from transits caused by planets. The result will be a rich database on EBs. The community will have access to the archive for uses such as for EB modeling of the high-precision light curves. A guest observer program is also planned for objects not already on the target list. [ABSTRACT FROM AUTHOR]

The space experiment Gaia, the approved cornerstone 6 ESA mission, will observe up to a billion stars in our Galaxy and obtain their astrometric positions on a microarcsec level, multi-band photometry as well as spectroscopic observations. It is expected that about one million Eclipsing Binaries (EBs) (with V ≤ 16 mag) will be discovered and the observing fashion will be quite similar to Hipparcos/Tycho mission operational mode. The combined astrometric, photometric and spectroscopic data will be used to compute the physical parameters of the observed EBs. From a study of a small sample of EBs, it is shown that the agreement between the fundamental stellar parameters, derived from ground-based and Hipparcos (Gaia-like) observations, is more than satisfactory and the Gaia data will be suitable to obtain accurate binary solutions. [ABSTRACT FROM AUTHOR]

The space experiment CoRoT will provide continuous monitoring and high accuracy light curves of about sixty thousand stars. Selected binary systems will be observed in the Additional Program frame as targets of long and continuous pointed observations. Moreover, thousands of new binaries will certainly be detected and hundreds of them will have extremely accurate light curves. This will allow studies of fine effects on the light curves, monitoring of stellar activity and, in combination with ground-based observations, will provide exquisite determination of stellar parameters. Among the new discoveries of interesting systems of special value will be those of low mass binaries. [ABSTRACT FROM AUTHOR]

UV and X-ray space-based interferometry will open unprecedented possibilities for spectral and spatial studies of a wide range of currently unresolvable interacting systems. Ultra-high angular resolution direct imaging of individual components and transport processes in interacting binary systems is essential for detailed studies and modeling of accretion and activity. Understanding the mass loss characteristics of both components, and the dynamics of the system as a function of time, will provide key inputs to evolutionary models and will revolutionize our view and understanding of the Universe. [ABSTRACT FROM AUTHOR]

We describe an automated method for assigning the most likely physical parameters to the components of an eclipsing binary (EB), using only its photometric light curve and combined color. In traditional methods (e.g. WD and EBOP) one attempts to optimize a multi-parameter model over many iterations, so as to minimize the chi-squared value. We suggest an alternative method, where one selects pairs of coeval stars from a set of theoretical stellar models, and compares their simulated light curves and combined colors with the observations. This approach greatly reduces the EB parameter-space over which one needs to search, and allows one to determine the components' masses, radii and absolute magnitudes, without spectroscopic data. We have implemented this method in an automated program using published theoretical isochrones and limb-darkening coefficients. Since it is easy to automate, this method lends itself to systematic analyses of datasets consisting of photometric time series of large numbers of stars, such as those produced by OGLE, MACHO, TrES, HAT, and many others surveys. [ABSTRACT FROM AUTHOR]

Eclipsing binary stars are gratifying objects because of their unique geometrical properties upon which all important physical parameters such as masses, radii, temperatures, luminosities and distance may be obtained in absolute scale. This poses strict demand on the model to be free of systematic effects that would influence the results later used for calibrations, catalogs and evolution theory. We present an objective scheme of obtaining individual temperatures of both binary system components by means of color-index constraining, with the only requirement that the observational data-set is acquired in a standard photometric system. We show that for a modest case of two similar main-sequence components the erroneous approach of assuming the temperature of the primary star from the color index yields temperatures which are systematically wrong by ∼ 100 K. [ABSTRACT FROM AUTHOR]

We present a new algorithm, the Eclipsing Binary Automated Solver (EBAS) to analyse lightcurves of eclipsing binaries. To replace human visual assessment, we introduce a new ‘alarm' goodness-of-fit statistic that takes into account correlation between neighbouring residuals. We apply the new algorithm to the whole sample of 2580 binaries found in the OGLE photometric survey of the LMC and derive the photometric elements for 1931 systems. To obtain the statistical properties of the short-period binaries of the LMC we construct a well defined subsample of 938 eclipsing binaries with main-sequence B-type primaries. Correcting for observational selection effects, we derive the distributions of the fractional radii of the two components and their sum, the brightness ratios and the periods of the short-period binaries. Somewhat surprisingly, the results are consistent with a flat distribution in log P between 2 and 10 days. [ABSTRACT FROM AUTHOR]

The method of spectra disentangling is reviewed in context with related techniques. New generalizations (disentangling with constraints) and applications (for spectroastrometry) are also described. [ABSTRACT FROM AUTHOR]

Recent theoretical calculations of stellar evolutionary tracks for rotating high-mass stars suggests that the chemical composition of the surface layers changes even whilst the star is evolving on the Main Sequence. The abundance analysis of binary components with precisely known fundamental stellar quantities allows a powerful comparison with theory. The observed spectra of close binary stars can be separated into the individual spectra of the component stars using the method of spectral disentangling on a time-series of spectra taken over the orbital cycle. Recently, Pavlovski and Hensberge (2005, A&A, 439, 309) have shown that, even with moderately high line-broadening, metal abundances can be derived from disentangled spectra with a precision of 0.1 dex. In a continuation of this project we have undertaken a detailed abundance analysis of the components of another two high-mass binaries, V453 Cyg, and V380 Cyg. Both binaries are well-studied systems with modern solutions. The components are close to the TAMS and therefore very suitable for an observational test of early mixing in high-mass stars. [ABSTRACT FROM AUTHOR]

With the advent of 8-12m-class telescopes and powerful new spectrographs, we can now extend the Doppler-imaging technique to the cool (and faint) end of the main sequence. At a spectral type of approximately M2, stars are thought to become fully convective and cannot possess an overshoot layer between a radiative core and a convective envelope which, as in the case of the Sun and similar stars, likely harbors the dynamo. Therefore, one could expect a fundamentally different magnetic-field topology than on the Sun and thus a qualitatively different surface temperature distribution with new, hitherto unknown, magnetic activity phenomena. Unfortunately, most single M stars do not rotate sufficiently fast for Doppler imaging and one has to "use" binaries or pre-main-sequence stars in which M stars appear spun up or, in binaries, synchronized to the orbital motion. [ABSTRACT FROM AUTHOR]

The short-period binary radial velocity program at the David Dunlap Observatory is described in some detail, with a brief summary on its history. The program is now reaching its 100-th orbit, with about 40 more orbits remaining within our access to Northern (δ > −15), bright (<10 mag), short-period (<1 day) binary systems. All data are processed uniformly using the Broadening Function (BF) formalism which offers best information extraction and permits analysis of heavily rotationally blended spectra. Many close binaries appear to have visual or spectroscopic companions. [ABSTRACT FROM AUTHOR]

One of the main pathways by which massive runaways are thought to be produced is by the disruption of a binary system after the supernova (SN) of one of its components. Under such a scenario, the populations of runaway stars in different phases should reflect the input binary population and its evolution. Conversely, if the system stays together after the SN, a High Mass X-Ray Binary (HMXB) may result. We present simulations exploring the behaviour of such runaway and HMXB populations with metallicity, and compare them to observations. As many as two-thirds of massive runaway stars may be produced by supernovae in binaries. Decreasing metallicity lowers the fraction of O stars which are runaway, but increases the Wolf-Rayet runaway fractions and the number of potential HMXBs. [ABSTRACT FROM AUTHOR]

In order to explain pre-eclipse dips at phases ∼0.7 in light curves of cataclysmic variables, the hypothesis of the thickening at the outer edge of the accretion disk is usually used. Shock-free nature of the interaction between the stream and the steady-state disk in the stationary solution poses the question on the cause of the of matter presence at significant height above the accretion disk in systems of this type. The results of 3D modeling have shown that in the absence of direct collision between the stream and the disk the formation of thickening of the halo above the disk is also possible. In the framework of the hot line model the significant part of the matter gets the acceleration in vertical direction. Gas movement in the vertical direction together with its movement along the outer edge of the disk leads to the gradual increase of the near-disk halo width. Maximum of the calculated thickening located above the outer part of the disk corresponds to the ∼0.7 phase that is in agreement with the observed values for cataclysmic variables with steady-state disks. This fact confirms the hot line model suggested earlier for description of the flow structure in semi-detached binaries and gives new opportunities for the interpretation of the light curves of such systems. [ABSTRACT FROM AUTHOR]

We present time-resolved optical spectroscopy of the famous X-ray binary SS 433. We obtained 61 medium resolution spectra spread over three months and thus cover roughly five orbits and about half a precession phase. We used various emission lines, that we attribute to the accretion disc, to determine the radial velocities of the compact component. They are of course modulated with the orbital period but in addition show a variation of the system velocity on a longer time scale. With the present data it is not possible to determine whether this is a transient effect or a periodic variation, although we present various possible interpretations of this effect. [ABSTRACT FROM AUTHOR]

We present a brief review of the recent results in modeling physical processes in strongly irradiated atmospheres of unevolved companions in precataclysmic binary systems (PCB) and their light curves. Constraints on physical parameters of the hot sdws primaries, thermal instability in upper irradiated atmosphere, monochromatic albedos, the deficit of the total emergent flux compared to the incoming flux from hot sdw primary are briefly discussed. [ABSTRACT FROM AUTHOR]

Line profiles and radial velocity curves for optical stars in X-ray binaries are calculated taking into account ellipticity of the optical star and X-ray heating effect. [ABSTRACT FROM AUTHOR]

In the last few years Chandra observations have revolutionized the study of X-ray binaries by extending observed samples to extragalactic distances and stellar environments of varied star formation history. Here we summarize some of our results related to the interpretation of current observations of young star clusters and of elliptical galaxies. [ABSTRACT FROM AUTHOR]

The DI Herculis system has been extensively studied over the past few decades because its observed rate of apsidal advance is less than a quarter of that which is expected from its physical and orbital properties. Work by Khaliullin et al. (1991) proposed that this slow rate of apsidal advance is a result of the presence of a third (stellar mass) body orbiting the system, however, observations by Guinan et al. (1994) severely restrict the orbital properties of such a solution. We show that a planetary mass object in a highly inclined orbit relative to the binary is capable of producing the observed apsidal motion, while remaining within the bounds of the most recent set of observations. A wide range of stable solutions are possible. [ABSTRACT FROM AUTHOR]

The most puzzling property of the extrasolar planets discovered by recent radial velocity surveys is their high orbital eccentricities, which are very difficult to explain within our current theoretical paradigm for planet formation. Current data reveal that at least 25% of these planets, including some with particularly high eccentricities, are orbiting a component of a binary star system. The presence of a distant companion can cause significant secular perturbations in the orbit of a planet. At high relative inclinations, large-amplitude, periodic eccentricity perturbations can occur. These are known as "Kozai cycles" and their amplitude is purely dependent on the relative orbital inclination. Assuming that every planet host star also has a (possibly unseen, e.g., substellar) distant companion, with reasonable distributions of orbital parameters and masses, we determine the resulting eccentricity distribution of planets and compare it to observations? We find that perturbations from a binary companion always appear to produce an excess of planets with both very high (≳0.6) and very low (e ≲ 0.1) eccentricities. The paucity of near-circular orbits in the observed sample implies that at least one additional mechanism must be increasing eccentricities. On the other hand, the overproduction of very high eccentricities observed in our models could be combined with plausible circularization mechanisms (e.g., friction from residual gas) to create more planets with intermediate eccentricities (e ≃0.1-0.6). [ABSTRACT FROM AUTHOR]

The OGLE survey for transiting planets has identified 177 transit candidates. Subsequent radial velocity follow-up of these candidates has allowed the detection of five transiting planets, as well as several dozen eclipsing binaries. Some of these systems consist of solar-type stars transited by small M dwarf companion, including the smallest stellar companions yet measured by transit. As a result, the OGLE transit survey has yielded a wealth of data on the mass-radius relation of planets and low-mass stars. In particular, two planet-sized stars were found, an empirical proof of the model predictions on Jupiter-sized main-sequence stars. [ABSTRACT FROM AUTHOR]

A project is presented which aims at high-precision determination of absolute parameters of close early-type eclipsing binaries in the LMC. We will use multi-object spectrographs (MOS) to measure RV curves of a large number of program stars selected from the MACHO archive. Spectroscopic mass ratios will be used as input for our light curve analysis code MORO. Application of the Simplex-based algorithm FITSB2 will achieve spectrum disentangling and fitting of NLTE model (TLUSTY) atmospheres, yielding orbital and atmospheric parameters. The method was extensively tested by application to time series of synthetic binary spectra for the expected range of S/N and MOS instrumental resolution. log g and Teff were reestablished with a precision of better than 5%, radial velocity amplitudes with errors of <3%. An important by-product of our project will be the improvement of the distance modulus of the LMC, a topic which is still being intensely discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The study of detached eclipsing binaries in open clusters can provide stringent tests of theoretical stellar evolutionary models, which must simultaneously fit the masses, radii, and luminosities of the eclipsing stars and the radiative properties of every other star in the cluster. We review recent progress in such studies and discuss two unusually interesting objects currently under analysis. GV Carinae is an A0m+A8m binary in the Southern open cluster NGC 3532; its eclipse depths have changed by 0.1 mag between 1990 and 2001, suggesting that its orbit is being perturbed by a relatively close third body. DW Carinae is a high-mass unevolved B1V + B1V binary in the very young open cluster Collinder 228, and displays double-peaked emission in the centre of the Hα line which is characteristic of Be stars. We conclude by pointing out that the great promise of eclipsing binaries in open clusters can only be satisfied when both the binaries and their parent clusters are well-observed, a situation which is less common than we would like. [ABSTRACT FROM AUTHOR]

UBV photometric observations of the active binary star CG Cygnus have been presented and analyzed to obtain absolute parameters of both components. Updated O-C diagram analysis by Kalimeris method yielded the values of 1.55×10−6 day and 1.4×10−7 day as the amplitudes of orbital period modulation, and Pmod1 ∼ 52.3 yr and Pmod2 ∼ 15.9 yr as the modulation periodicities. Finally, the consequences of period changes have been discussed on the basis of Applegate mechanism. [ABSTRACT FROM AUTHOR]

To synthesise images of stellar photospheres with high spot filling factors, we model an extrapolated solar size distribution of spots on an immaculate SV Cam. These models of starspot coverage show that the primary star is peppered with a large number of subresolution spots. Using these model starspot distributions we generate a photometric lightcurve, which is then used as input to an maximumentropy eclipse mapping code, that is based on chi-squared minimisation. I solve for the system parameters to show the effect of dense spot coverage on the derived system parameters, and show that surface brightness distributions reconstructed from these lightcurves have distinctive spots on the primary star at its quadrature points. It is concluded that two-spot modelling or chi-squared minimisation techniques are more susceptible to spurious structures being generated by systematic errors, arising from incorrect assumptions about photospheric surface brightness, than simple Fourier analysis of the light-curves. [ABSTRACT FROM AUTHOR]

The number of confirmed and suspected close T Tauri binaries (period days) is increasing. We discuss some systems with enhanced emission line activity and periodic line profile changes. Non-axisymmetric flows of plasma in the region between the circumbinary disk and the stars can be generated through the influence of the secondary component. Such enhanced activity is found around binaries with eccentric as well as circular orbits. We discuss our observations of the T Tauri stars RW Aurigae A and RU Lupi, which may host very close brown dwarf companions. Model simulations indicate that non-axisymmetric flows are generated around close binaries with circumbinary disks, also in systems with circular orbits. [ABSTRACT FROM AUTHOR]

We examine the positions of the active longitudes in close binaries with respect to their companion stars on a sample of 12 systems. The primaries of four (five?) main sequence eclipsing binaries (RT And, CG Cyg, BH Vir, WY Cnc, and, possibly, UV Psc) show active longitudes at the quadrature positions. The K2 IV component of RS CVn has spots at all longitudes. Three subgiant binaries (AR Lac, SZ Psc and RT Lac have spots on both components, with pronounced active longitudes at the substellar points, and at other longitudes as well. Finally, three giant, non-eclipsing binaries (UZ Lib, HK Lac, IM Peg) have active longitudes at their substellar points and opposite to it. In case of main sequence systems probably their common magnetic field, for giants the tidal force, and, for subgiants both forces together, determine the positions of the active longitudes. [ABSTRACT FROM AUTHOR]

Intensive monitoring of main-sequence stars for pulsational studies continuously reveals new binaries and multiple systems. The resulting extensive data sets lead to exact orbital parameters, and to accurate masses of the components. This is also the case higher up the main sequence, though less frequently. We discuss a few examples where intensive observational efforts are necessary in order to improve our knowledge of the pulsational behaviour in the upper main-sequence instability domains, but we emphasize that observational efforts alone that turn out more and more of the same type of data, are by far insufficient, and that there is urgent need for theoretical developments. Determination of highly accurate stellar parameters is of paramount importance and is much more needed than time-series observations. [ABSTRACT FROM AUTHOR]

Orbital period changes of the eclipsing binaries GO Cyg and GW Cep are explained by the light-time effect for the first time. New minima of the eclipsing binary AR Aur improve the predicted light-time orbit. The light-time orbit with the quadratic ephemeris of the binary matches the new observations of V505 Sgr better than the linear one. As the light-time effect fits in corresponding O − C diagrams of all four systems have been reaching extreme values, the observations of minima times in forthcoming years are highly desirable. [ABSTRACT FROM AUTHOR]

Eclipsing binaries with M-type components are still rare objects. Strong observational biases have made that today only a few eclipsing binaries with component masses below 0.6 M⊙ and well-determined fundamental properties are known. However, even in these small numbers the detailed comparison of the observed masses and radii with theoretical predictions has revealed large disagreements. Current models seem to predict radii of stars in the 0.4-0.8M⊙ range to be some 5-15% smaller than observed. Given the high accuracy of the empirical measurements (a few percent in both mass and radius), these differences are highly significant. I review all the observational evidence on the properties of M-type stars and discuss a possible scenario based on stellar activity to explain the observed discrepancies. [ABSTRACT FROM AUTHOR]

BAT99-129 is a rare, short-period eclipsing Wolf-Rayet binary in the Large Magellanic Cloud. We present here medium-resolution NTT/EMMI spectra that allow us to disentangle the spectra of the two components and find the orbital parameters of the binary. We also present VLT/FORS1 spectra of this binary taken during the secondary eclipse, i.e. when the companion star passes in front of the Wolf-Rayet star. With these data we are able to extract, for the first time in absolute units for a WR+O binary, the sizes of the line emitting regions. [ABSTRACT FROM AUTHOR]

It is argued that typical W UMa-type stars are old, advanced evolutionary objects, similar to Algols, in the sense that they are past mass exchange resulting in a mass ratio inversion. Their secondaries are oversized due to depletion of hydrogen, and in many cases they possess small helium cores. An alternative evolutionary scenario leading to such a configuration is presented. Differences between the evolution of binaries with the initial mass ratio far and close to unity are discussed. [ABSTRACT FROM AUTHOR]

When three point masses form a hierarchical triple system, the short-period orbit can be severely modified by the long-period orbit if the two orbits are inclined to each other by more than about 39°deg (sin−1 √2/5). Such an inclination can induce ‘Kozai cycles' (Kozai, 1962), in which the eccentricity of the inner orbit cycles by a large amount while its period and therefore semimajor axis remains roughly constant. During those periastra when the eccentricity is largest, tidal friction may become important, and this can result in a secular shrinkage of the orbit, until it becomes circularised at a period of a few days. However, apsidal motion due to either GR or to the quadrupolar distortion of the components (if they are no longer treated as point masses) can reduce the range of eccentricity. We explore the limits on outer and inner orbital period that these perturbations imply. If the components are F/G/K/M dwarfs, then rotationallydriven dynamo activity can become important at the short periods that can occur in the right circumstances. It can cause the period to shorten further. The result may be a contact binary, and/or a merger in which the two stars of the inner pair coalesce to form a single rapidly rotating star. We suggest that this may be the origin of AB Dor, a very rapidly rotating K dwarf that is probably about 50 Myr old. [ABSTRACT FROM AUTHOR]

UBV light-curves of the eclipsing binary HS Herculis, obtained in 2002-2003 observational seasons, were analysed with Wilson-Devinney computer code. New absolute dimensions of the system were calculated using the results of the light-curve analysis. Period variation of the system was also investigated. Several new times of minima have been secured for this problematic system. An apsidal motion with a period of 80.7 years was confirmed and a third body in a pretty eccentric orbit (e3 = 0.90 ± 0.08) with a period of 85.4 years was found. The corresponding internal structure constants of the binary system, logk2, and the mass of the third body were derived. [ABSTRACT FROM AUTHOR]

The formations of the blue straggler stars and the FK Com-type stars are unsolved problems in stellar astrophysics. One of the possibilities for their formations is from the coalescence of W UMa-type overcontact binary systems. Therefore, deep (f > 50%), low-mass ratio (q < 0.25) overcontact binary stars are a very important source to understand the phenomena of Blue Straggler/FK Com-type stars. Recently, 12 W UMa-type binary stars, FG Hya, GR Vir, IK Per, TV Mus, CU Tau, V857 Her, V410 Aur, XY Boo, SX CrV, QX And, GSC 619-232, and AH Cnc, were investigated photometrically. Apart fromTV Mus, XY boo, and GSC 619-232, new observations of the other 9 binaries were obtained. Complete light curves of the 10 systems, FG Hya, GR Vir, IK Per, TV Mus, CU Tau, V857 Her, GSC 619-232, V410 Aur, XY Boo, and AH Cnc, were analyzed with the 2003 version of the W-D code. It is shown that all of those systems are deep (f > 50%), low-mass ratio (q < 0.25) overcontact binary stars. We found that the system GSC 619-232 has the highest degree of overcontact (f = 93.4%). The derived photometric mass ratio of V857 Her, q = 0.0653, indicates that it is the lowest-mass ratio system among W UMa-type binaries. Of the 12 sample stars, long-term period changes of 11 systems were found. About 58% (seven) of the sample binaries show cyclic period oscillation. No cyclic period changes were discovered for the other 5 systems, which may be caused by the short observational time interval or by insufficient observations. Therefore, we think that all W UMa-type binary stars may contain cyclic period variations. By considering the long-term period changes (both increase and decrease) of those binary stars, we proposed two evolutionary scenarios evolving from deep, low-mass ratio overcontact binaries into Blue Straggler/FK Com-type stars. [ABSTRACT FROM AUTHOR]

Analytical formulae for the computation of the photometric elements of extra-solar planetary transits are presented. They were initially derived for the study of well-detached eclipsing binaries and are valid for any degree of limb darkening and type of transit as well as for eccentric orbits. The only assumption is that the projections of the star and the planet on the plane of the sky are well represented by circular discs. The procedure to get valid ranges for the involved parameters, as well as to make precise estimations of initial parameters, using the analytical nature of the equations is given together with some discussion on their practical application. Examples are shown for OGLE-TR-113, representative of a light curve obtained with ground-based telescopes, and HD 209458 with a precise light curve obtained with the Hubble Space Telescope. [ABSTRACT FROM AUTHOR]