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1.
In this paper, we give theBV photoelectric light curves of the Algol-type eclipsing binary EU Hydrae. We have analysed its period by means of the times of minima determined from this observation and the times of minima which other observers published. The period was found to gradually decrease with a change rate dP/dE = -3 . d 29 × 10–10. The obtained light curves have been solved using Wilson-Devinney's synthetic light-curve program. The results demonstrate that EU Hydrae is a detached system, the secondary component fills the Roche-lobe, its mass ratio is 0.205. EU Hya may evolve to be a semidetached system in which the secondary component fills the Roche-lobe.  相似文献   

2.
It is shown that the erratic changes of the orbital period, which are observed in some detached eclipsing binary systems, cannot be interpreted as real if their light curves show changing anomalies with asymmetric minimum profiles. In this case the photometrically determined times of the minima do not coincide with the ideal geometric ones, which are unobservable. This fact and the applied reduction methods for deriving the photometric times of minima cause systematic period errors of cumulative character. The discussion of six photoelectrically-determined minima obtained within the last 20 yr, and earlier photographic ones of the 0d.479 period eclipsing binary XY UMa yields a constant period. The long cyclic light curve variations due to starspot activity of the larger and hotter component of this system are reflected in corresponding period oscillations. Dedicated to Dr. Ida Noddack on the occasion of her eightieth birthday.  相似文献   

3.
Many available published times of light minima of the late-type binary system ER Vul have been compiled and analyzed using a new method proposed by Kalimeris et al. (1994). It was shown that the orbital period of the system oscillation with a period of about 30.6 years and an amplitude of 3.2×10-6 days while it undergoes a constant period decrease of about dP /P=7.84× 10-8 day / year. The prospective physical mechanisms that could have modulated the orbital period behaviour (periodic or non-periodic), have been studied. We found that a combination of a magnetic activity cycle mechanism and an enhanced stellar wind could explain satisfactorily the period change.  相似文献   

4.
The period study of the eclipsing binary system GH Pegasi has been presented for the first time. A new period (P=2d.556135) of GH Peg, based on all available times of minima, has been given. O–C diagrams of the system have also been presented for the first time, and the period changes present in the system have been analysed. The period shows changes around the year 1972 and 1981. The total period change in different portions of the O–C diagram, based on the corrected period, ranges from 5.2×10–6 d to 7.0×10–5 d. The photoelectric minima show sufficiently large scatter in the system.  相似文献   

5.
The period study of the eclipsing binary DF Hya, based on up-to-date minima has been presented. The least-squares method has been applied to obtain a new period, which comes out to be 0 . d 3306017. Period changes are found around the years 1949, 1974, and 1982. Appreciable period changes are apparent around 1949 and 1974, the strongest being around 1974. The period changes (P) range from 0.46×10–6 d to 0.46×10–5 d, the average being 1.89×10–6 d. Such period changes are usual for a contact system, like DF Hya. Our results do not show increase in the time interval 1959–1985 as suggested by Zhanget al. (1989).  相似文献   

6.
New photoelectric UBV observations were obtained for the eclipsing binary TT Her at the Ankara University Observatory (AUO) and three new times of minima were calculated from these observations. The (O – C) diagram constructed for all available times of minima of TT Her exhibits a cyclic character superimposed on a quadratic variation. The quadratic character yields an orbital period decrease with a rate of dP /dt = –8.83 × 10–8 day yr–1 which can be attributed to the mass exchange/loss mechanism in the system. By assuming the presence of a gravitationally bound third body in the system, the analysis of the cyclic nature in the (O – C) diagram revealed a third body with a mass of 0.21M⊙ orbiting around the eclipsing pair. The possibility of magnetic activity cycle effect as a cause for the observed cyclic variation in the (O – C) diagram was also discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
B andV photometry of DM UMa obtained between January, 1980 and June, 1984 is presented. Analysis yields a mean photometric period 7d.478±0d.010, compared to the known oribital period of 7d.492±0d.009. Light curves obtained during any two seasons do not agree in any of the following: shape, amplitude, phases of the light maxima and minima, mean light level, or brightness at the light maxima and minima. From the change inB-V over the photometric period, we concludethat the hemisphere visible during the light minimum is cooler than that seen during light maximum. The mean colorB-V=1m.065±0m.002 is consistent with K1 III or K2 IV. Phases of light minima lie on two well-separated groups with different slopes; the corresponding periods are 7d.471±0d.002 and 7d.481±0d.001, in dicating that both migrate linearly towards decreasing orbital phase. In terms of the starspot model this indicates that two respective centers of activity were situated at different longitudes and latitudes on a differentially rotating star. From circumstantial evidence we infer that the dark region seen from 1979 onwards disintegrated sometime between the 1982 and 1983 observing seasons, leaving behind an area of relatively high surface brightness. We can put a lower limit of about four years on the lifetime of a center of activity.  相似文献   

8.
A new period (P=2 . d 9042997) of the eclipsing binary system VZ Hydrae has been given, which is based on all the available times of minima. The period based on the photoelectric epochs has also been presented. The O?C diagram and detailed period study of VZ Hya have been presented for the first time, and the period changes have been estimated in different portions of the O?C diagram. Significant period changes do not appear to have occurred in VZ Hya, however, the O?C diagram suggests that the period of the system shows a slow tendency to increase. Period changes of 10?5 d (?) to 10?7 d have occurred around the years 1933, 1971, and 1975. All four period changes are noted in the time-interval 1918 to 1978. Upward treands appear stronger than the declining trends. Secondary minima show larger fluctuations than the primary minima. The fluctuations of the O?C values around the zero-line of VZ Hya demands notice for searching out the cause of period variations such as the presence of a third body.  相似文献   

9.
A first detailed period study of the eclipsing RS CVn-binary system RW Com is presented. A new period (P=0d.2373455) based on 223 minima is given. The O–C diagrams of RW Com have been presented for the first time. Types of ten minima have been corrected judging the period trend. Period changes in different portions of the O–C diagram (Figure 2) have been estimated. The total change in period (P/P) ranges from 5.5×10–7 to 6.4×10–6. Thus, P ranges from 1.3×10–7 d to 1.5×10–6 d. Numerous minima are available in the time interval 1967 to 1986. This part of the O–C diagram (Figure 2) shows a sinusoidal variation, thus, it is suspected that RW Com could be a three-body system. The period of variation due to third body appears to be nearly 16 years.  相似文献   

10.
We present a new set of CCD photometric observations for the short period eclipsing binary 1SWASP J1743 (= V1067 Her). We have determined the available times of light minima and two new linear and quadratic ephemerides have been obtained. The photometric solutions for the system have been performed using Wilson and Devinney Code. The 3D and fill out configuration revealed that V1067 Her is an over contact W UMa binary with relatively low fill-out factor of about 16%.We investigated the period variation for the system. It showed a strong evidence of period changes by using the (O-C) residual diagram method and we have concluded long-term orbital period decrease rate dP/dt= −3.0 × 10−7 d/yr, corresponding to a time scale 8.6 × 105 yr. Such period decrease in the A-type W UMa systems is usually interpreted to be due to mass transfer from the more to the less massive component.  相似文献   

11.
B andV observations of the W Ursae Majoris-type eclipsing variable system AK Her were made on five nights at the Ege University Observatory. Several times of minima were obtained during the observations and the new light elements were calculated. The light-time period was found to be about 75.72 years. The light curve of the system appears to change in each cycle for both colours. The secondary minimum of the system seems to be a total eclipse with a duration of about 42 m .5.  相似文献   

12.
The RS CVn-type eclipsing binary star MM Her has been observed in two colours,B andV, in 1979, 1980, and 1983. Several minima times were obtained during the observations and new light elements calculated. The light curves of the system obtained in blue and yellow lights show a significant wave-like distortion which migrates towards the decreasing orbital phases. Its migration period was estimated to be about 3.5 yr. The amplitudes of the wave-like distortion inB andV appear to change each year. The primary minimum of the system is a total eclipse with a duration of 0d.08.  相似文献   

13.
Two-colour photoelectric observations of the short-period RS CVn-type eclipsing binary UV Psc have been made between 1981–1986 at the Ege University Observatory. The present work deals with the light curve variations of the binary obtained in the observing seasons of 1981, 1982, and 1984. The shape of the light curve, the depths of the minima, and the total brightness of the system seemed to change in the course of time that covers three years of observing time. The value of the migration period of the wave-like distortion was roughly estimated to be between 1.5 and 2.0 years.  相似文献   

14.
Photometric and high resolution spectroscopic data for the Herbig star HD 52721 obtained from October 2009 through October 2010 are presented. We confirm the cyclical character of the photometric variability of HD 52721 discovered previously by others. The variability shows up as minima in the light curve of this star which repeat with a period P = 0d.805 and are typical of eclipsing binary systems. ASAS data covering an observation period from September 2003 through December 2009 show that two neighboring photometric minima differ from one another, and the actual orbital period of the system must be twice as high (P = 1d.610). This is confirmed by the spectroscopic data. These show that the center of gravity of the emission Hα line and the profile of the HeI 6678 line with a distinct, bright circumstellar component have a clear correlation with a period of 1d.610. To all appearances, HD 52721 is a close binary system consisting of two class B2 stars with quite similar parameters. We propose that the observed cyclical variations in the circumstellar parameters may be related to the existence of a global azimuthal inhomogeneity within the shell which rotates synchronously with the orbital motion of the system components.  相似文献   

15.
Detailed period study of the eclipsing binary system Delta Cap is presented. Available times of minima have been classified, and two minima have been found off the instant period trend. A new period of 1.d0227789 has been given. Period changes in different portions of the O?C diagram have been estimated, which range from 6.4×10?6 d to 1.8×10?3 d (?), the average being 3.5×10?5 d. A sinusoidal variation is evident in the O?C diagrams, which is indicative of the possible presence of a third body, having a period of nearly 62 years, however, it is yet to be confirmed.  相似文献   

16.
Over four hundred photoelectric observations of U Peg in B and V were secured with a 0.6M reflector at Beijing Observatory in 1978. Four times of minima were determined. A period study of the times of minima from 1896 to 1980 was performed. The system was found to have a secular period decrease, Δp/p of ?1.32 ¢ 10?1 or ?4.16 × 10?3 sec/yr, as well as a short term (17 years) sinusoidal oscillation with a semi-amplitude of 0.00323 day. It is suggested that oscillating term is caused by the light-time effect of an unseen third body. The third body may be a M6 main sequence star with a mass of 0.16 M⊙. The longterm secular change in period may be associated with slow mass transfer.The analysis of the 1978 light curves together with the 1958 light curves of Binnendijk suggest that the system U Peg has an overcontact configuration of about 9%. It has the characteristics of a W-type W UMa system. The photometric mass ratio, m2m1, is between 3 and 2.5. If we correct the Struve et al. γ-velocity from 0 km/sec to about ?40 km/sec the estimated spectroscopic mass ratio would agree with the photoelectric value. Based on the above assumption the absolute dimensions of U Peg are of 0.6 and 1.8 M⊙ and of 0.8 and 1.4 R⊙, for components 1 and 2 respectively. The physical dimensions indicate that the components are main sequence stars.  相似文献   

17.
In this study we present photometric observations of the eclipsing binary KR Cyg made in 1999 and 2000. The observations of the eclipsing binary KR Cyg have been carried out in B, V and R colours at the Ege University Observatory. A new seasonal light curves are presented. New times of minima and ephemerides are given. Based on a statistical analysis of the times of minima obtained by photoelectric photometry, the orbital period of the system is found to be constant. The photometric mass ratio of the system is well determined. The corresponding light curves were analyzed by the Wilson-Devinney code. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

18.
The new period (P=0 . d 461700) of the eclipsing binary system DX Aqr has been presented, which is based on available times of minima. O–C diagram of DX Aqr has been presented for the first time, and the period variations present in the system have been analysed. In all five period increases and five period decreases are nothed, and four period increases and five period decreases have been discussed. The strongest period increase occurs between 1975 and 1976. The total period change in different portions of the O–C diagram ranges from 1.40×10–4 d to 3.61×10–6 d. Appreciable period fluctuations have been noted to have occurred in the time intervals, 1964–1965 and 1974–1975.  相似文献   

19.
A slightly improved period (P=0 . d 7408401) of the eclipsing binary system TX Ceti has been given, which is based on all available times of minima. The O-C diagrams based on the period given in PPEN (1980) and based on the new period, have been given. The period of TX Ceti shows fair constancy between the time interval 1928 to 1988. The present O-C diagrams do not confirm, either the presence of a third body or the presence of mass transfer as suggested earlier.  相似文献   

20.
Photometric BV light curves of BO CVn obtained in 1992 and new times of minima are presented. The primary minimum shows a transit, whereas the secondary minimum, shows an occultation. The system may be classified as an A‐type W UMa system. A complete study of minima allows one to detect a possibly increasing period by about 0.037 s/yr. This indicates that the conservative mass transfer rate from the less massive component to the more massive one is 1.57 10—10M⊙ /yr. Because of the variable period, the new ephemeris is determined for future observations. Using the Wilson‐Devinney code a simultaneous solution of the B and V light curves is also performed. The analysis shows that the system is in a contact configuration with q = 0.205 ± 0.001 and fillout factor (f) = 0.18, T1 = 7240 K (fixed), T2 = 7150± 10 K. The high orbital inclination i = 87°.54 ± 0.26 was con firmed by photometric observations of the secondary minimum.  相似文献   

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