Analysis of the light curves of SX Aurigae,by automated fourier techniques

The aim of the present paper has beento analyse the light changes of the close eclipsing system SX Aurigae in the frequency-domain. This analysis is based on Kopal's new theory recently developed for the study of light variations, between minima as well as within eclipses, of close eclipsing binaries whose components are distorted by axial rotation and mutual tidal action.A method for the separation of the photometric proximityand eclipse effects directly from the observed data is also presented. In this method no rectification is needed. The automated method has been tested on the light curves of SX Aurigae. Finally, a comparative discussion is given of Kopal and Kitamura methods of thelight curves analysis.     

Geometrical and physical elements of four β Lyrae type eclipsing variables

The aim of the present paper is to present the analysis of light changes of four Lyrae eclipsing systems (DO Cas, KR Cyg, V388 Cyg, and SV Cen) using the automated Fourier techniques in the frequency-domain.The applicability of the above method to the Lyrae system discussed. New physical and geometrical elements of these systems are derived. Their positions in the H-R diagram and mass-luminosity diagram are indicated.     

Analysis of the light curves of PV Cassiopeiae by use of automatized fourier techniques

UBV Light Curves of the eclipsing binary system PV Cassiopeiae have been investigated using recently developed frequency-domain techniques. This analysis is based on Kopal's new theory for the study of the light variations, between minima as well as within eclipses, of eclipsing binaries whose components undistorted or distorted by axial rotation and mutual tidal action.A method for the distinguishing of the photometric proximity and eclipse effects directly from the observed data is also presented. In this method no rectification is needed. The automated method has been tested successfully on the light curves of PV Cassiopeiae. Finally, a comparative discussion is given of Kopal's and Kitamura's methods of the light curves analysis.     

Analysis of the light curves of SZ Cam using automatized fourier techniques

UBV light curves of the early type close eclipsing binary system SZ Cam have been investigated using recently developed frequency-domain techniques. The combination of both minima in the analysis results in a distinct methodological improvement over the single minimum method discussed hitherto. This improvement has two aspects: (i) increased accuracy of the determined elements, (ii) agreement of the results of the two-minimum method with those of the single-minimum method provides a criterion whereby the self-consistency of the underlying model with its representation of the light curve in the regions between minima by a cosine series and the empirically determined coefficients of such a series may be assessed. Such a self-consistent solution is found, and a further step towards a realistic representation is made by including the photometric perturbations. It is confirmed from these three light curves that the less massive star is overluminous. A probable tendency for the limb-darkening coefficient of the more massive star to increase with decreasing wavelength is also noted.     

Fourier analysis of the light curves of eclipsing variables,XIX

The aim of the present paper has been to generalize the methods previously developed for analysis of the light changes of eclipsing binary systems in the frequency-domain to cases in which the components of such systems revolve in eccentric orbits. It is shown that these methods can indeed be generalized to systems with eccentric orbits provided that the light momentsA _2m deduced from such eclipses are suitably re-defined in terms of the true, rather than mean, anomaly in the relative orbit; and that due attention is paid to the unit of length in terms of which the fractional radii of the two stars are expressed. When this is done the Fourier methods continue to be applicable to all types of eclipses exhibited by eccentric binary systems — whether these are occultations or transits; total, annular or partial.An application of these methods to practical cases has been postponed for a subsequent communication.     

On the evaluation of the photometric proximity effects of close eclipsing systems

The aim of the present paper has been to generalize the method, developed by Kopal (1976), for the evaluation of the photometric proximity effects (between minima as well as within eclipses) of distorted eclipsing systems. The method is extended to quantities of second order (n-7) is surficial distortion. Analytical expressions of the polynomials to be used for modulation of the light curve are also given.     

An analysis of the light changes of the eclipsing system AK Herculis in the frequency domain

The aim of the present paper has been to analyse the light changes of the close eclipsing system AK Herculis in the frequency domain. This analysis is based on Kopal's new theory recently developed for the study of light variations—between minima as well as within eclipses—of close eclipsing binaries whose components are distorted by axial rotation and mutual tidal action.A new method for the separation of the photometric proximity and eclipse effects directly from the observed data is also presented. In this method no rectification is needed. New elements taking into account the photometric perturbations are also given.     

Analysis of the light curves of RT Persei by automatized fourier techniques

A new method has been developed by Kopal (1977c, Paper XII) to make use of expressions for the fractional loss of light ₀ ^l of the arbitrarily limb-darkened stars in the form of Hankel transforms of zero-order, in order to evaluate the explicit forms of the ₀ ^l s for different types of eclipse, as well as of the momentsA _2m of the respective light curves in a closed form. The automated method has been tested successfully on the light curves of RT Persei. Also, a photometric curve fit of RT Persei is investigated by application of numerical quadratures to determine the theoretical light curve appropriate for the Roche model. Finally a comparative discussion is given of various methods of light curve analaysis.On leave from Department of Physics, University of Ferdowsi, Mashad, Iran.     

Spectroscopic investigation of a birefringent Lyot-filter for Hα

The instrumental profile of a Lyot-filter with 0.5 Å pass-band for H has been determined from photographic spectra obtained with a large grating spectrograph and a continuous light source.After fine adjustment of the filter, the transmission profile in parallel light agrees closely with the theoretical profile as given by crystal optics. The peak transmission has been found to be 12% of the incident unpolarized radiation.Convolving the measured instrumental profile with the average solar spectral distribution near H, it can be shown that the parasitic light (transmission outside the main pass-band) contributes 10% to the total light flux with the filter centered on the line. At wavelength shifts of 0.5 and 0.8Å, the parasitic light contribution is 25% and 40%, respectively.The deformation of the line-profile of various solar phenomena (faculae, filaments, flares) by the instrumental profile is discussed quantitatively.Mitteilungen aus dem Fraunhofer Institut Nr. 82.     

The gravity-darkening of highly distorted stars in close binary systems

From a quantitative analysis of the photometric ellipticity effect, values of the exponent of gravity-darkening have been empirically deduced for the components of sixteen W UMa systems with accurate cross-correlation spectroscopic mass ratios. In the analysis, the exponents for both components of a W UMa system are assumed to be the same. In view of the generally unstable nature of their light curves and the consequent difficulty to find an unique set of the fractional radii of both components, -values have been derived for various equipotential surfaces with boundary cases set at the inner and outer Roche lobes.The results indicate that if the fill-out factors are less than 0.5 (as is so for most of the actual cases), the deduced -values are all greater than Lucy's conventional value of 0.32. The empirical -values as a whole are found to increase with the mean effective temperature of the components and, furthermore, they show a tendency to decrease with increasing mass ratio, particularly for A-type systems. Thus, a W UMa system consisting of two components of quite different masses has a large empirical -value. These observational evidences indicate that the structure of the photosphere of contact components of W UMa systems is significantly different from that of normal Main-Sequence stars of similar spectral type and may provide a clue to solve puzzles of W UMa stars.     

Analysis of the light curves of V78 in ω Centauri in the frequency domain by automatized fourier techniques

The aim of the present paper has been to analyse the light changes of the close eclipsing system V78 in Centauri in the frequency domain. In two of his recent papers, Kopal (1977b, c) has developed new methods for the analysis of light curves using Hankel transforms of zero order. He succeeded in expressing the momentsA _2m of light curves in a closed form. The expansions, in terms of which the momentsA _2m can be expressed, converge in all circumstances. Their analytical structure presents no difficulty for automatic computation. The light variations of the eclipsing system V78 in Centauri have been studied by use of the above method. New geometrical elements are also given.     

Test computations on the dynamical evolution of star clusters

Test calculations have been carried out on the evolution of star clusters using the fluiddynamical method devised by Larson (1970a). Large systems of stars have been considered with specific concern with globular clusters. With reference to the analogous standard model by Larson, the influence of varying in turn the various free parameters (cluster mass, star mass, tidal radius, mass concentration of the initial model) has been studied for the results. Furthermore, the partial release of some simplifying assumptions with regard to the relaxation time and distribution of the target stars has been considered. The change of the structural properties is discussed, and the variation of the evolutionary time scale is outlined. An indicative agreement of the results obtained here with structural properties of globular clusters as deduced from previous theoretical models is pointed out.     

Computation of the elements of close eclipsing systems in the frequency-domain

The aim of the present paper will be to generalize the methods for computation of the elements of eclipsing binary systems in the frequency-domain, summarized in our recent Paper I (Kopal, 1981), to the case ofclose systems, in which photometric proximity effects become conspicuous and must be taken into account before the methods previously outlined in Paper I become directly applicable.Following a brief introduction to the subject given in Section 1, Section 2 summarizes (and comments upon) the difficulties previously encountered in separation of the photometric proximity and eclipse effects. In Section 3 we develop an alternative new approach to the problem by modulation of the light curves throughout the entire orbital cycle, intended to filter out proximity effects from the observed light changes and isolate those due to eclipses; while in Section 4 we shall present a numerical application of the new method to an analysis of the observed light changes of the eclipsing system W Ursae Maioris.In Section 5 we shall present a quantitative investigation of the photometric effects of distortion on the light changes of close eclipsing systems within eclipses-the most complicated part of the whole problem-with numerical application to the system of U Sagittae carried out in the concluding Section 6.Appendices 1–3 contain numerical data which should facilitate application of the methods developed and illustrated in Sections 3–4; while Appendix 4 will be reserved for a mathematical proof of certain expansions used in Section 5, which would have been too discursive for the main text.     

ESOSAT and IUE observations of the symbiotic binary R Aquarii during maximum and minimum

Coordinated IUE and EXOSAT observations of the symbiotic Mira R Aqr, made in June and December 1985, at phases 0.0 and 0.5 of the Mira light curve, are discussed. A weak X-ray flux has been for the first time unambiquously detected without any significant change with the Mira light curve. Also the UV spectrum of the central object has not varied, while the presence of high ionization lines (NV and HeII) in the spectrum of the jet-like feature is confirmed. The data are discussed in the light of a model in which the jet is preexisting material illuminated by the recently increased X and UV radiation from the inner edge of the accretion disk around the degenerate companion of the Mira primary.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Synthetic light curves of two eclipsing binary systems,U Sge and AW UMa

Photometric curve fits have been investigated by means of numerical quadratures to develop theoretical light curves appropriate to stars built up in accordance with the Roche model. The method has been applied previously to β Per (Al-Naimiy and Budding, 1977) on the basis of available observations in red and infrared, while presently applied to two systems with contact components.

1. U Sge, spherical primary totally eclipsed by a contact component secondary. Improved photometric elements of the system have been found, and compared with those obtained by Kopal's method in the frequency domain. The outcome of the curve fitting corresponds well with the results of an analysis in the frequency domain.
2. AW UMa, exhibiting the shallowest minima known for totally eclipsing W UMa systems. The physical and geometrical elements of the system have been found, and the contact nature of the two components confirmed.

     

Obscuration in the direction of the IC 1318 a,b, c,nebular complex

The extinction of light caused by the presence of dust along the IC 1318 nebular complex has been investigated by comparing optical (H) data of high photometric accuracy and radio data of the same angular resolution. The role of the detected dust condensations in the formation of stars has also been discussed.     

Frequency domain light curve analysis of partially eclipsing binary systems: With an application to β Persei (Algol)

Kopal's new iterative method for analysing partially eclipsing binary light curves in the frequency domain has been put into a form suitable for applications, and explicit forms for basic expressions developed. To facilitate the computations in practice, the required newS _m -functions, which are expressed in terms ofJ _, ⁰ -integrals, have been extensively tabulated by making use of hypergeometric series. The automated method has been tested successfully on the light curves of Persei (Algol). Short information on the system and the revised sets of elements including a new determination of the limb-darkening coefficient in the ultraviolet have been presented.     

Note on the analysis of light curves of eclipsing binaries with dissimilar components

The term l _per giving a correction needed to reduce the light curves of eclipsing binaries with dissimilar components to those of rectifiable models with similar components is discussed in view of a practical definition of the luminosities of the components. A new form of the term is proposed. Furthermore, a way is shown for applying this term also when the light curve has already been rectified in the usual manner.Mitteilung des Astronomischen Instituts der Universität Tübingen Nr. 108.     

Observations and analysis of the Southern binary R Arae

This paper investigates the nature of the relatively bright ( 7th magnitude) eclipsing variable R Arae (HD 149730A), which has an orbital period of 4^d.42509, from the analysis of photometricUBV observations. The main objective behind such an analysis is to determine whether the system qualifies for a classical Algol of semi-detached status.An analysis has been performed twice on each of theUBV curves as well as the light curve due to Gaposchkin, utilising a light curve optimisation procedure. In the first analysis the presence of the visual companion (HD 1497330B) to R Arae (angular separation = 3'.6), whose light was present in all observations, was not accounted for. The second analysis attempts to account for this third light source.All the analyses indicate the relative radius of the secondary star, is of the order of 0.20. This value is well below the limit which would classify the system as a semi-detached binary.These results do, however, seem to be somewhat discordant with the spectroscopic and general photometric nature of the system, all of which suggest mass transfer processes to be occuring (therefore a possible semi-detached status). This is seen in several features, especially a marked increase in the system's mean orbital period, which tends to corroborate mass transfer from the secondary star.     

Fourier techniques for an analysis of eclipsing binary light curves: I

The Fourier techniques developed so far for an analysis of eclipsing binary light curves have been re-discussed. The Fourier coefficients for the analysis have been derived in a simple form of series expansions, in terms of eclipse elements, valid for any type of eclipse (regardless of whetherr ₁r ₂).These coefficients may be utilized to solve the eclipse elements in terms of the observed characteristics of the light curves. A general relation between the observed quantitiesl and , and the eclipse elementsr _1,2,i andL ₁ has also been given in the form of series expansions which can be used for the synthesis of the light curves.