Synthetic light curve solutions for the short-period eclipsing binaries ST Aqr,DO Cas,and TX Cet

Synthetic light curve solutions of the short-period binary systems ST Aqr, DO Cas, and TX Cet are presented. Their evolutionary state is briefly discussed.     

食双星V375 Cas的光电测光研究

本文给出了首次食双星V375 Cas的BV两色光电测光资料和新的历元,并用Wilson-Devinney综合光变曲线方法取得测光解。结果表明:V375 Cas是一个类似RZ Dra的早型半相接双星系统,小质量子星充满了临界等位面,而大质量子星几乎充满了临界等位面,此星对于了解早型密近双星的演化是很有意义的。     

Photometry of the contact binary system V471 Cas

UBV photoelectric observations of the W UMa-type binary V471 Cas were made from September to November 1984. Its colour indices were found to be(B-V)=0 _. ^m 771±0 _. ^m 02 and(U-B)=0 _. ^m 196±0 _. ^m 02. TheU, B, andV light curves of V471 Cas show some photometric fluctuations. We found that its orbital period is not 0.335998 days which was given by GCVS (1986), but 0.405356 days.Photometric orbital elements of V471 Cas were found using the Wilson-Devinney method. V471 Cas is a contact system, in which the overcontact factor is 0.19, its mass ratio of two components is 0.5947, and orbital minclination is in 83.29 degrees.     

The system of DO cassiopeiae: Photoelectric observations and light curves analysis

The newB andV photoelectric observations of DO Cas, obtained during 1979 and 1980, are presented, analysed, and discussed. The observations were made at the National Observatory of Athens, Greece, and their analysis was based on the frequency domain, techniques. New geometric, photometric, and absolute elements for the system are given.     

An analysis of the orbital periods of some eclipsing binaries suspected to be in the pre-main sequence contraction phase of evolution

An analysis of the available photoelectric times of minima of KO Aql, TV Cas and Z Her, which are suspected to be in pre-main sequence phase of evolution, reveals that KO Aql shows a secular increase in its orbital period at the rate of 4·34 × 10⁻⁸ day per cycle while the period of TV Cas has been decreasing at the rate of 4·08 × 10⁻⁹ day per cycle. Z Her does not show any period change at all. The orbital period of any binary system which is in the pre-main sequence phase will be systematically affected because of ′ shrinking′ dimensions of the components. A simple formula for the characteristic period change, defined by (P/P), is derived from a consideration of the conservation of total energy and total angular momentum for a binary system whose components are still in the process of contraction or expansion. The derived formula is applied to the above systems to see whether theoretical characteristic period changes agree with the observed values. The systems are assumed to evolve independently in the pre-main sequence phase in accordance with the model calculations of Iben (1965). It is found that there is no agreement between theoretical and observed characteristic period changes. This suggests that KO Aql and TV Cas may not be in the pre-main sequence phase. We do not have sufficient data for Z Her to judge its evolutionary status by the present procedure; this is also true of TT Hya. We suspect that the period changes observed in KO Aql and TV Cas may be due to light-time effect.     

Photometric elements of V364 cassiopeiae

TheUBV photometric observations of the eclipsing binary V364 Cas have been discussed. Two sets of photometric elements, one based on the Russell and Merrill methods and the other based on Kopal's new method of the analysis of the light curves of eclipsing binary stars in the frequency-domain, have been derived. Using the observed colour indicesU-B andB-V, the spectral types of the systemic components are estimated. An examination of all the available times of minimum light of V364 Cas does not reveal any change in its orbital period.     

Photometric study of MM Cas

TheU, B, andV photometric observations of the eclipsing binary MM Cas have been presented and discussed. The photometric elements have been derived. By use of the colour indicesU-B andB-V, the spectral types of the systemic components are estimated. An examination of all available times of minimum light of MM Cas does not reveal any change in its orbital period.     

B and V photometry and analysis of the eclipsing binary RZ Cas

Photoelectric light curves of the eclipsing binary RZ Cas are presented forB andV filters. The light curves are analysed for light and geometrical elements, starting with a previously suggested preliminary method. The approximate results thus obtained are then optimised through the Wilson-Devinney computer programs.     

Bm Cas: A Long-Period Eclipsing Binary with A Supergiant and a Common Envelope

New results of UBVR photometry of the long-period eclipsing binary BM Cas obtained at Tallinn Observatory between 1979 and 1996 are discussed.     

First ground‐based photometry and light‐curve analysis of the eccentric eclipsing binary V744 Cas

The first ground‐based BVR photometric observations of the recently discovered eclipsing binary V744 Cas are presented. From these measurements, timings for two primary and one secondary minima have been calculated. The light curves of the system were analyzed by using the Wilson‐Devinney program. The analysis shows that the system is detached with two similar components of spectral type A2V, and the orbit is eccentric (e = 0.0662 ± 0.0005). The longitude of the periastron (ω) was found significantly different for two different light curves (ours and that of Hipparcos), which is strongly suggestive of an apsidal motion with a period of about 425 ± 68 yr. This makes V744 Cas an important candidate for studies of apsidal motions. The first estimate of the absolute dimensions place the system close to the terminal age of the main sequence (TAMS) in the HR diagram. The distance from the spectroscopic parallax (d = 740 ± 10 pc) was found to be slightly larger than the Hipparcos distance of d = 610 ± 400 pc. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoelectric and visual observations of AM Cas

According to statistical informations the orbital period of this cataclysmic binary of Z Camelopardalis type should be in the range between 0^d.10 and 0^d.19. A sole deep minimum was found photoelectrically. It lasted about 40 minutes and had an amplitude of nearly 2 mag in U. For reasons described in detail it can hardly be interpreted as an eclipsing one. Possibly there is no contribution to the light variation of AM Cas from orbital motion.     

The early-type eclipsing contact binary TY Puppis

In this paper we present theBV photoelectric light curves of the W UMa-type eclipsing binary TY Pup. We have gained ephemerides by means of the times of minima. The obtained light curves have been solved using Wilson-Devinney's synthetic code. The results indicate that TY Pup is a contact system with mass ratio 0.185 and a large degree of overcontact of 52%. Combined with spectroscopic material, absolute parameters of TY Pup are derived. It may be concluded that TY Pup is an evolved contact binary.     

High excitation emission lines in binary systems with roundchroms

An unexpected empirical fact, a dependence of the observed luminosities inhigh excitation emission lines – 1240 NV, 1400 SiIV, 1550 CIV, 1640 HeII– on the intercomponent distance a of RS CVn type close binary systems,is revealed. It is assumed that those high excitation emission lines aregenerated most probably in a cone-like region between the Lagrangian pointL ₁ and the surface of the primary component of the system. Thebehavior of high excitation emission lines at various phases of theeclipse in the case of two binary systems, SX Cas and 22 Vul, indicatesthe possibility of existence of such a `Lagrangian cone' in the structureof common chromospheres – roundchroms – of close binary systems as amain source of generation of high excitation emission lines.     

Preliminary study of light variations of the eclipsing binary AB Cassiopeiae

Preliminary study of the eclipsing binary AB Cas is presented here by using the photometric observational data. The primary component is one of the Sct variables with period of 0^d.054, and whether the oscillation is of a radial mode or of a non-radial one is discussed. Two colour indices (B-V andU-B) data and the light curve analysis suggest that this binary system is a typical Algol type binary system, in which the primary component is near the ZAMS with about 2.3M and the secondary one is a subgiant star with about 0.5M .     

Determination of two groups of high luminosity red variable stars

Based on analysis of photometric, colorimetric, and polarimetric data, we show that red variable stars of high luminosity are divided with respect to their period of brightness variation into two groups: I) binary stars with periods larger than 480 days; II) single stars with periods less than 480 days. The binary stars exhibit: a) large correlation coefficients between the V-band brightness variation and the U-B, B-V colors; b) comparatively smaller U-B colors (< 1. ^m 5);c)strong variability of polarization parameters. Based on this division, we suspect that the star PZ Cas is a binary.Translated from Astrofizika, Vol. 37, No. 2, pp. 235–244, April–June, 1994.In conclusion, the author wishes to express deep gratitude to professor L. V. Mirzoyan for valuable comments.     

Revision of the photometric parameters of BS Cassiopeiae

Seven charge-coupled device(CCD)photometric times of light minimum of the overcontact binary BS Cas which were obtained from 2007 August to November and one CCD light curve in the R band which was observed on 2007 September 24 and October 15,are presented.It is found that the light curve of BS Cas has characteristics like a typical EW-type light variation.The light curve obtained by us is symmetric and shows total eclipses,which is very useful for determining photometric parameters with high precision.Photometric solutions were derived by using the 2003 version of the Wilson-Devinney code.It shows that BS Cas is a W-subtype overcontact binary(f = 27.5% ± 0.4%)with a mass ratio of q = 2.7188 ± 0.0040.The temperature difference between the two components is 190 K.Analysis of the O-C curve suggests that the period of AE Phe shows a long-term continuous decrease at a rate of dP/dt=-2.45 × 10-7 dyr-1.The long-time period decrease can be explained by mass transfer from the primary to the secondary.     

Velocity curve analysis of the spectroscopic binary stars RZ Cas,CC Cas,HS Her,HD 93917, V921 Her and Y Cygni by the artificial neural networks

We use an Artificial Neural Network (ANN) to derive the orbital parameters ofspectroscopic binary stars. Using measured radial velocity data of six double‐lined spectroscopic binary systems RZ Cas, CC Cas, HS Her, HD 93917, V921 Her and Y Cygni, we find corresponding orbital and spectroscopic elements. Our numerical results are in good agreement with those obtained by others using more traditional methods (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

New CCD photometry for the extreme lower mass-ratio binary AW Ursae Majoris

This paper presents charge-couple device (CCD) photometric observations for the eclipsing binary AW UMa. The V-band light curve in 2007 was analyzed using the 2003 version of the Wilson–Devinney code. It is confirmed that AW UMa is a total eclipsing binary with a higher degree of contact f=80.2% and a lower mass ratio of q=0.076. From the (O−C) curve, the orbital period shows a continuous period decrease at a rate of dP/dt=−2.05×10⁻⁷ d yr⁻¹. The long-term period decrease suggested that AW UMa is undergoing the mass transfer from the primary component to the secondary one, accompanied by angular momentum loss due to mass outflow L ₂. Weak evidence indicates that there exists a cyclic variation with a period of 17.6 yr and a small amplitude of A=0. ^d 0019, which may be attributed to the light-time effect via the third body. If the existence of an additional body is true, it may remove a great amount of angular momentum from the central system. For this kind of contact binary, as the orbital period decreases, the shrinking of the inner and outer critical Roche lobes will cause the contact degree f to increase. Finally, this kind of binary will merge into a single rapid-rotation star.     

Orbital Period Changes of Two Very Short-Period W UMa Stars CC Com and V523 Cas: A Possible Evidence for TRO Plus AML Model

Orbital period changes of the two very short-period contactbinaries, CC Com and V523 Cas, are presented. It is shownthat the period of CC Com varies in secular decrease withrate of dP/dt = –4.39 ×10^-8 days/year, while theperiod of V523 Cas is increasing at rate of dP/dt =+9.09 ×10^-8 days/year. The physical parameters of the twoW UMa stars are nearly equal which indicates that the physicalproperties of the two contact binaries are almost the same.The different types of period changes in the two systemsmay strongly suggest that, although they are undergoingsecular angular momentum loss (AML), the oscillatory characterpredicted by thermal relaxation oscilation (TRO) theory stillexist and they are on the different TRO stages, i.e., CC Comis on the shrinking TRO stage, but V523 Cas is on the expendingTRO stage. The present period changes of the two systems can beexplained by the combination of the TRO and the AML theories.     

Velocity curve analysis of the spectroscopic binary stars by the non-linear least squares

We introduce a new method to derive the orbital parameters of spectroscopic binary stars by a non-linear least squares analysis of residuals. Using measured radial velocity data of four double lined spectroscopic binary systems RZ Cas, CC Cas, V1130 Tau and Y Cygni, we find corresponding orbital and spectroscopic elements. Our numerical results are in good agreement with those obtained by others using more traditional methods.