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1.
The eclípsing binary AR Lac has been observed in two colours,B andV, in 1980 and 1981. The new times of minimal obtained during the observatons indicate that the period of the system is still continuing its decrease. The wave-like distortions outside eclipses have two maxima and are very similar in shape in successive two years.  相似文献   

2.
The RS CVn-type eclipsing binary SZ Psc was observed in two coloursB andV, in 1981. The rate of change of the period was calculated using two different least-squares procedures. The amplitudes of the light variations at outside eclipses are 0 . m 181 and 0 . m 213 inB andV colours, respectively. The light curves of the system have been solved using a new approximation. The radius of the cooler component is only 82% of its Roche-radius and the system is detached one.  相似文献   

3.
The RS CVn-type eclipsing binary star RT Lac has been observed inB andV colours, during 1984, 1985, 1986, 1987, and 1988 observing seasons. The orbital period of the system was found to be decreasing with an amount of 62 s century–1. The brightnesses both at minima and maxima are changing with time. It seems that the variations of the brightnesses at mid-primary and second quarter are similar, but at second first quarters are opposite to each other. We believe that these variations are mainly related with the spots (or spot groups) located on the surface of the component star which is in front during the primary minimum. We also estimate the period of the spot activity cycle to be approximately six years.  相似文献   

4.
The RS CVn-type eclipsing binary AR Lac has been observed in two colours,B andV, in 1978 and 1979. Several times of minima have been obtained during the observations and the new light elements have been calculated. The orbital period of the system was found to be decreasing with an amount of 14.6 s century–1.The light curves of the system obtained inB andV show a significant wave-like distortion outside eclipses. The amplitudes of the wave-like distortion inB andV are about 0 . m 09 and 0 . m 10 in 1978, and, 0 . m 12 and 0 . m 13 in 1979, respectively. The minima of the wave-like distortion have shifted with an amount of 0 . p 40 in one year, thus indicating the migration period of the wave-like distortion is about 2.5 yr.A noticeable variation of light during the totality of primary minimum has also been observed. This variation can be attributed to the distortion wave which has been moving towards decreasing phases.  相似文献   

5.
PhotoelectricB andV observations of the W UMa-type system OO Aql have been obtained for 11 nights during the period from 22 June–30 July, 1987. A total of 978 observations were obtained in eachB andV filter. All these observations were transformed to theB andV colours of theUBV standard system. Five light curves for primary and secondary eclipses were obtained, its times of minima were determined and a new linear ephemeris was given. The period changes of the system were discussed.  相似文献   

6.
The RS CVn-type eclipsing binary MM Her was observed photoelectrically inB andV colours. The light curves obtained in 1984 and 1985 are presented. It was found that the depths of the primary minima are decreased from 1983 to 1985. However, the amplitude of the wave-like distortion outside the eclipses was detected to increase since 1976. The period of migration was determined to be about 3.57±0.08 years.  相似文献   

7.
SW Lacertae is a short-period variable star of the W UMa-type. A total of 261 photoelectric observations for eachU, B, andV filter were obtained in 1986 while 522 photoelectric observations for eachB andV filter were obtained in 1987. All these observations were transformed to theU, B, andV colours of theUBV standard system. Nine light curves for primary and secondary eclipses were obtained, their times of minima were determined and a new linear ephemeris was obtained. The period changes of the system were also discussed.  相似文献   

8.
Sinusoidal variations in bothV - andB-bands were detected in some flare stars of the UV Ceti type outside of flares. This detection has confirmed the light variation detection in Johnson'sV -band in EV Lac at quiet-state luminosity by Pettersen (1980) with a cyclic period equals about 4 . d 378 and an amplitude of about 0 . m 07. An interpretation of these short cyclic periods is that they are due to intensity modulations from a photospheric spot group as a result of stellar equatorial rotations. A short period of 14 days with an amplitude of 0 . m 099 was detected inB-band in AD Leo. For the two flare stars, BD+55° 1823 and DO Cep in bothV- andB-bands, cyclic periods of more than 3 days and less than 17 days with amplitudes more than 0 . m 090 and less than 0 . m 250 have been registered. A significant contribution has been found in the flare star EV Lac in bothV- andB-bands at its quiescent-state luminosity where the detected cyclic periods are agreed with that which was detected by Pettersen (1980) in the same flare star in Johnson'sV-band, about 4 days. Furthermore, we found the same cyclic period in the colour index,B - V (about 4 days) which strengthens starspot phenomenon. This colour index period could not be detected by Pettersen (1980).  相似文献   

9.
Photometric observations of eclipsing binary star XY UMa have been presented. The light curve analysis have been carried out on two colours,B andV, by inferring as much information as possible about the sarr from other published data and then synthesizing light curves and comparing them with our own observations.The light fluctuations of outside eclipses caused by intrinsic light variation of primary component have been obtained by deconvolution of the theoretical light curve from observed one. It has been shown that the intrinsic light variation of primary component can be interpreted in terms of cool star-spot covering 8% of the stellar photosphere.Finally, the significance of star-spot has been discussed.  相似文献   

10.
The W UMa-type systems (OO Aql, V839 Oph, V566 Oph, and SW Lac) were observed photoelectrically in two wavebands (B andV) during the years 1982–1983. The light curves of these systems are analysed using Kopal's frequency-domain technique and the optimisation method. New geometrical and physical elements have been determined. The absolute elements and the period variations of these systems are discussed.  相似文献   

11.
Photoelectric and absolute elements of the system RT Per have been determined inU, B, andV filters. It is suggested that the primary star may be surrounded by a gaseous disk.  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.
The W UMa-type system V839 Oph was observed photoelectrically in two wavebands (B andV) during 1985 at the Kryonerion Astronomical Station of the National Observatory of Greece. The light curves of the system are analysed using the frequency-domain techniques and new geometric and photometric elements are given. The light variations of the system are also discussed.  相似文献   

14.
B andV observations of the eclipsing binary RU Eridani made on 23 nights during 1974–76 are reported. An improved period of 0d.63219951 is derived. After rectification ofB andV light curves, new elements are derived using Russel-Merrill method. The system is classified as semidetached.  相似文献   

15.
Photoelectric observations of the bright eclipsing binary system HU Tauri are presented. The observations were made with standardB andV filters. Observations made during the eclipses yielded six epochs of minimum light. A study of all the available times of minimum light has been made. Analysis of all the photoelectric times of minimum light yielded the following new ephemeris: JD 2441275.3166 +2 . d 0563107E. Asymmetries in the light curves of HU Tauri were noticed.  相似文献   

16.
This paper presents results of our monitoring of BL Lac at the 2.56 m Nordic Optical Telescope in La Palma and at the 0.91 m telescope at National Astronomical Observatory in Dodaira, Japan. On La Palma we used aUBVRI-photopolarimeter which gives truly simultaneous observations in all five colour bands. At Dodaira we used a photopolarimeter which gives simultaneously photometry atB, V andR-bands and polarimetry atV-band. We have observations of BL Lac during flare behaviour and during these times we have observed a clear rotation of the polarization position angle. During these flares the polarization level has also been strongly variable and the object has lost its preferred direction of the polarization position angle. The reason for this behaviour remains still unclear, but there are two possible explanations: shocks in the helical magnetic field in the jet pointing nearly towards us or polarized synchrotron flares rotating within the accretion disk (seen nearly face on) of the supermassive central black hole.  相似文献   

17.
In an attempt to discover planetary eclipses, we observed the open cluster NGC 7086. On one night we observed the cluster and standard stars through the B and V filters, enabling us to make a colour-magnitude diagram. Plots of the differential magnitudes were inspected for variability, but no planetary eclipses were found. New variable stars were discovered and their light curves show some of them to be eclipsing binary stars. The location on the colour-magnitude diagram of some of the variable stars is consistent with cluster membership.  相似文献   

18.
A light variation in Johnson'sV-band of flare star EV Lac has been registered by Pettersen (1980). The cycle length was 4 . d 378 with amplitude about 0 . m 07. A Fourier analysis programme has been applied on our measured data of the flare star BD+55°1823 in Johnson'sV andB bands. A period of 16d and amplitude of 0 . m 14 have been detected in theV-band.  相似文献   

19.
In 1992 UBV photometry of short period binary system UV PSc were presented. The results obtained from the analysis ofU, B andV light curves represent transit solutions. The light fluctuations of out-side eclipses have been interpreted in terms of cool star-spots on the photosphere of the primary component. Its parameters have been determined.  相似文献   

20.
The W UMa-system U Pegasi was observed photoelectrically in two wavebands (B andV) in 1984. The light curves of this system are analysed using Kopal's frequency-domain technique and the optimisation method. New geometrical and physical elements have been determined and the period-variations discussed.  相似文献   

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