The light curve variations in UV piscium

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.     

1992 UBV observations of UV piscium and light curve analysis

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.     

Two-colour photoelectric investigation of AR Lacertae

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.     

Two-colour photoelectric investigation of SZ Pisces

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.     

The distortion wave on the light curve of the RS CVn binary UV piscium

The eclipsing binary UV Piscium was observed with the standardUBV filters during 1976-77, 1977-78 and 1978-79 observing seasons with the 1.22-m reflecting telescope of the Japal-Rangapur Observatory. A wave-like distortion on the light curve noticed by Carr (1969), Oliver (1974), Sadik (1979) and Zeiliket al. (1982a) is confirmed by the present observations. Combining our observations with those of Carr, Oliver and Sadik, it is found that the distortion wave is moving towards decreasing orbital phase with a period of about 1200 days. The source of the observed distortion wave is found to be the hotter component.     

Five-color photoelectric photometry of asteroid 433 Eros

Five-color photoelectric lightcurves of asteroid 433 Eros were obtained on 9 nights during the 1974/75 apparition. Although color differences due to changing solar phase angle were detected, color differences during a single rotation of Eros are less than 1%. Amplitudes of up to 1^m.44 were measured, and there are indications that three reversals in the relative depths of the two minima occured between late December 1974 and late January 1975. The absolute visual magnitude at primary maximum, corrected to zero phase and to one AU from Earth and Sun, is about V₀(1,0) = 10^m.8.     

BVRI photometry and light curve analysis of VW CEP

Synthetic light curve solutions for the W UMa-system VW Cep have been determined by applying the most new version of Wilson (1998)approach to B-observations of 1996 and VRI-observations of 1999. From a consideration of the possible evolution of this system, it is found that the system is a partial eclipsing contact one, and its primary to be a nearly Main-Sequence F5 star of mass 0.85 M _⊙ and the secondary to be a dwarf of spectral type G0 of mass 0.34 M _⊙. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photometry of the RS CVn type eclipsing binary UV piscium

The analysis of the UBV photoelectric study of the short period RS CVn eclipsing binary, UV Psc, has suggested that the primary is a transit with _e=27°,i=88 _. ^o 5, andk=0.75. The spectral type and luminosity of the hotter component is estimated to be G4-6V and that of the cooler component to be K0-2V. Absolute dimensions for the components of UV Psc were derived by combining the present analysis with that of the spectroscopic analysis given by Popper.The out-of-eclipse observations have showed large amount of scatter and an investigation of this showed that hotter component could be an intrinscic variable. No periodicity for this variation has been fixed due to lack of sufficient data.Paper presented at the Lembang-Bamberg IAU Colloquium No.80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.     

Cyclic light and period variations of the UV Leonis system

Solutions of the new standard V‐light curves for the EA type binary UV Leo are obtained using the PHOEBE code (0.31a version). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the absolute magnitude‐color (l.e. M_V vs. B – V) isochrones diagram, based on which the age of the system is estimated to be >4×10⁹ yr. Also times of minima data (“O – C curve”) have been analyzed. Apart from an almost sinusoidal variation with a period of 29.63 yr, which modulates the orbital period, and was attributed to a third body orbiting around the system, other cyclic variation in the orbital period and also brightness, with time scales of 24.25 and 22.77 yr were found, respectively. We associate this with a magnetic activity cycle newly reported here for UV Leo (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multicolour photoelectric photometry of the open cluster NGC 752

In the open cluster NGC 752, 89 stars are observed in the Vilnius seven-colour photometric system, including probable members fainter than observed hitherto. Spectral classification of observed stars are made and individual reddening values are determined. The mean reddening of the cluster stars is equivalentE(B - V) = 0 _. ^m 025. By fitting on colour index-magnitude diagrams the cluster Main Sequence with the Hyades one the distance modulus (m - M)₀ = 8 _. ^m 15 ± 0 _. ^m 15 is found. For 11 red giant members of the cluster absolute magnitudes are derived and compared with ones of the standard calibration. It is obtained that the cluster giants are in mean 0 _. ^m 6 fainter than giants of corresponding spectral class in the solar vicinity.     

New photoelectric observations and light curve analysis of 44i bootis

The eclipsing binary 44i Boo was observed photoelectrically using the 40 cm Cassegrain telescope at the Al-Battani Observatory.The light curves were analysed using Fourier techniques of light changes in the frequency-domain, and new geometrical and physical elements have been obtained.A new active period to be started in 1986 has been observed.     

B-V photoelectric photometry of white-dwarf eclipsing binary V471 Tauri

Photoelectric photometry of the unusual binary system, whose light curve shows peculiar light variations, has been done in the two colours. The observations obtained at the Ege University Observatory between 1973 and 1978 and at the Kottamia Observatory in November 1977 show a variable light curve. The observed variations in the light curve show a migrating wave towards a decreasing orbital phase similar to those observed in RS CVn-binaries. The migration period appears to be about 191 days. The times of minima indicate that there has been a decrease on the orbital period of the system. However, since there is not enough material on the observed times of minima, we cannot explain whether the decrease in the orbital period has been sudden or gradual. The radii of the components have been computed from the primary minimum alone. With the available spectroscopic data, the absolute dimensions of the components are also presented. It appears to be difficult to explain the evolution of the system without taking into consideration the mass loss. The proposed models for the evolution of the system and an explanation of the observed light variations are also presented.     

Analysis of the photoelectric light curve and the orbital period variations of the binary system UU Andromedae

In this work, the analysis of the photoelectric light curve (LC) in the broad‐band filter (400–700 nm) for the UU And system was carried out using the PHOEBE program (vers. 0.31a). The absolute dimensions of the system are determined and its evolution is discussed. Moreover, the period changes of the system are studied using updated O – C data, which shows a cyclic change with a period of P_mod = 18 yr. This was attributed to a magnetic activity cycle operating in this system. In addition to the cyclic change, a long‐term secular variation due to mass transfer from the secondary to the primary component with a rate of 6.17×10^–9 M_⊙ yr^–1 was also detected. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solar irradiance variations from photometry of active regions

The Extreme Limb Photometer (ELP) has been used to measure the irradiance fluctuation of the Sun due to selected active regions. Forty-five active regions that were completely scanned at various disk positions are included in the analysis. The contribution of these active regions to a global solar irradiance fluctuation has been correlated with photometric sunspot and facular indices (PSI and PFI) using published values of sunspot and calcium plage areas. The measured ELP fluctuations are converted to a global brightness fluctuation, B/B. The sunspot component of B/B correlates with PSI with r = 0.95. The facular component of B/B correlates with PFI with r - 0.72. The expression for PFI is important to the question of energy balance between sunspots and faculae and the results presented here are not incompatible with energy balance between the two phenomena; that is the energy deficit of sunspots may be balanced by the energy excess of faculae.     

Five-color photometry of Saturn and its rings

Analysis of 206 high-quality plates from three recent apparitions taken in five colors has yielded several photometric parameters for Saturn and its A and B rings. Phase curves and geometric albedos are derived for two regions of Saturn and for each ring. The phase coefficients of the rings are found to be independent of the ring-plane inclination angle. A comparison of the phase curves shows that the particles of ring A exhibit a larger phase coefficient than do those of ring B. When examined with a multiple-scattering model using Henyey-Greenstein phase functions, the observations of the ring tilt effect indicate that the particles of ring A may also have lower single-scattering and geometric albedos. The color dependence of the geometric albedo of the particles in ring B is shown to be very similar to that of Europa (J II). We find for ring A an optical thickness of 0.50 (0.45 ≤ τ_A ≤ 0.57) and for the Cassini division, 0.018 ± 0.004.     

Recent photoelectric photometry of the newly discovered eclipsing system BD + 13o4708

Two-colour photoelectric photometry of the eclipsing binary BD + 13^o4708 was carried out. Several features such as asymmetry in the branches, light difference between the maxima, an eccentric orbit, a dip around phase 0.2 are distinctive. The new light elements of the system were computed using also the previous times of primary minima given by Walker (1988).     

UBV photometry and light-curve analysis of Algol

Photoelectric observations of the eclipsing variable β Per, were obtained inUBV standard system, and new elements for the primary minimum were determined as $$J.D. = 2445641.5135,O - C = 0_.^d 0.009.$$ The light curves of the system were analysed using Fourier techniques in the frequency-domain. The fractional radii of both components are $$r_1 = 0.217 \pm 0.002,r_2 = 0.233 \pm 0.002andi = 85.5 \pm 0.5.$$ Absolute elements were derived and the effective temperatures are $$T_1 = 11800K,T_2 = 5140K.$$