A photometric study of V566 ophiuchi

The A-type W UMa system V566 Oph was observed photoelectrically in two wavebands (B andV) in the years 1988-1989 at the Kryonerion Astronomical Station of the National Observatory of Athens, Greece. The light curves of the system are analyzed using frequency-domain techniques and new geometric and photometric elements are derived. These elements are combined with the more recent spectroscopic data based on Reticon observations to yield the absolute parameters of the system. The evolutionary status of the system is considered and it is found that V566 Oph has started its evolution away from the Main Sequence. The period of the system continues to increase.     

A photometric study of the star V1016 Ori

New photoelectric UBVRI observations of the eclipsing variable V 1016 Ori have been obtained with the AZT-11 telescope at Crimean Astrophysical Observatory and with the Zeiss-600 telescope at Mount Maidanak Observatory. Light curves are constructed from the new observations and from published and archival data. We use a total of 340, 348, 386, 185, and 62 magnitude estimates in the bands from U to I, respectively. An analysis of these data has yielded the following results. The photometric elements were refined; their new values are $Min I = JDH 2441966.820 + 65\mathop .\limits^d 4331E$ . The UBVRI magnitudes outside eclipse were found to be $5\mathop .\limits^m 95$ , $6\mathop .\limits^m 77$ , $6\mathop .\limits^m 75$ , $6\mathop .\limits^m 68$ , and $6\mathop .\limits^m 16$ , respectively. No phase effect was detected. We obtained two light-curve solutions: (1) assuming that the giant star was in front of the small one during eclipse, we determined the stellar radii, r _s=0.0141 and r _g=0.0228 (in fractions of the semimajor axis of the orbit); and (2) assuming that the small star was in front of the giant one, we derived r _g=0.0186 and r _s=0.0180 for the V band. The brightness of the primary star in the bands from U to I is L ₁=0.96, 0.92, 0.90, 0.89, and 0.88, the orbital inclination is $i = 87^\circ .1$ , and the maximum eclipse phase is α₀= 0.66. In both cases, we accepted the U hypothesis, assumed the orbit to be elliptical, and took into account the flux from the star Θ¹ Ori E that fell within the photometer aperture. The first solution leads to a discrepancy between the primary radius determined by solving the light curve and the radial-velocity curve and its value estimated from the luminosity and temperature. This discrepancy is eliminated in the second solution, and it turns out that, by all parameters, the primary corresponds to a normal zero-age main-sequence star.     

A photometric study of the detached binary WY Hydrae with twin components

We present a multicolor photometry for the eclipsing binary WY Hydrae, observed on four nights of 2008 December. From our new observations and Carr’s data, the photometric solutions were deduced by using the updated W–D program. The results show that WY Hya is a detached binary with a mass ratio of q = 0.970(±0.005).By analyzing the O–C curve, it is found that there exists either a continuous period increase or a cyclic variation. From Eq. (2), the orbital period of WY Hya secularly increases at a rate of dP/dt = +3.56(±0.37) × 10^?7 days/yr, which may be interpreted by some mass transfer for the near-contact configuration or tidal dissipation. From Eq. (3), the period and semi-amplitude of the periodic oscillation are P₃ = 95.4(±4.2) yr and A = 0^d.0087(±0^d.0003), respectively. This may be likely attributed by light-time effect via the presence of the assumed third body. Assumed in the coplanar orbit with the binary, the mass of the third body should be M₃ = 0.18 M_⊙. If the unseen additional companion exists, it will extract angular momentum from the binary system. Finally, WY Hya with high fill-out factors (i.e., f_1,2 > 80%), may evolve into a semi-detached configuration.     

A photometric study of the eclipsing binary V 1073 Cygni

Photoelectric observations of the eclipsing binary V 1073 Cyg have been carried out inB andV colours at the Ege University Observatory. The light curves were analyzed with the Wilson-Devinney approach. A period study reveals that the orbital period of the system is decreasing at the rate of (3.21 ± 0.17) second per century.     

A photometric study of a weak-contact binary: V873 Per

We present a photometric study of a weak-contact binary V873 Per. New observations in BVR filter bands showed asymmetric light curves to be a negative type of the O’Connell effect, which can be described by magnetic activity of a cool spot on the more massive component. Our photometric solutions showed that V873 Per is a W-type with a mass ratio of q = 2.504(±0.0029), confirming the results of Samec et al. (2009). The derived contact degree was found to be f = 18.10%(±1.36%). Moreover, our analysis found the cyclic variation with the period of about 4 yr that could be due to existence of the third companion in the system or the mechanism of magnetic activity cycle in the binary. While available data indicated that the long-term orbital period tends to be stable rather than decreasing.     

A long-term photometric study of the pre-main-sequence star V 350 Cep

Results from photographic and CCD photometric observations of the pre-main sequence star V 350 Cep are presented. A continued gradual rise of brightness resembling the light curves of the FUOR type stars is observed. A search in the WFPDB was made to find old photographic observations of V 350 Cep.     

A photometric and spectroscopic study of the binary V1430 Aql

We present the first infrared light curves of the binary V1430 Aql, in the bands J and K, plus V, R and I light curves and spectra covering the ranges of H_β, H_α and Ca II-IRT lines. Our VRIJK data, together with published radial velocity curves, are analyzed to determine the orbital and stellar parameters of the system. Both stellar components present spectroscopic evidence of chromospheric activity, with emission excesses in the H_β, H_α and Ca II-IRT lines. The measured ratio of the lines H_β/H_α emission excesses can be interpreted as originated in plages. Our light curves also show photometric evidence of cool spots at least on one of the stars.     

A photometric study of the Algol system Y Piscium

From the discussion of 417 photoelectric observations of this semi-detached Algol system, obtained in B and V during 82 nights in 1965–1971, the existence of a gas stream may be inferred for the following reasons: The scatter of the single observations is dependent on the orbital phase; the largest scatter occurs at the phases following both eclipses. The conventional photometric solution which is based on the long region rectification and neglects the photometric influences of the gas stream, gives for the two colours different geometric parameters of the system. However, the short region rectification allows a consistent photometric solution. According to this solution a short total phase exists, and the luminous regions caused by the impact of particles of the gas stream are hidden during the central part of the primary eclipse. Outside of eclipses, the additional light is seen during about half of the orbital period. From the variation of the visibility of the additional light during the primary eclipse it may be concluded that during about the first half of the observing time the luminous regions were situated at the high latitudes of the bright component, indicating the existence of magnetic fields on this component at this epoch, whilst later on the additional light came from an equatorial region on the following side of the massive component.Originally presented at the IAU Colloquium No. 16 held at the Univ. of Pennsylvenia, Philadelphia Pa., U.S.A. September 8–11, 1971.     

A photometric study of the Algol system Y Hydri

297UBV observations of the Algol type eclipsing binary Y Hyi are presented and analyzed by a synthetic light curve technique. The system is semi-detached and shows complete eclipses.Based on observations collected at the European Southern Observatory, La Silla, Chile.     

First photometric study of the W UMa system GSC 1042-2191

We present new photometric observations covering eight minima times for the eclipsing binary GSC 1042-2191. The light curves in $\mathit{BVRI}$ colors were analyzed by using WD-code for the system parameters. Eight minima times were obtained from the new observations. The system is found a low mass ratio (q = 0.148), A-type over-contact binary with a fill out parameter of f = 65.01 ± 12.18%. The preliminary absolute dimensions (M₁= 1.26 ± 0.06 M_⊙, M₂ = 0.18 ± 0.06 M_⊙, R₁ = 1.54 ± 0.20 R_⊙, R₂ = 0.69 ± 0.01 R_⊙, ${\mathit{L}}_1$ =3.30 ± 0.30 L_⊙ and ${\mathit{L}}_2$ = 0.59 ± 0.20 L_⊙) indicate the very much oversized and over-luminous secondary component, by assuming the present luminosity of the secondary is its main sequence luminosity, we predict the original mass is about 0.8 M_⊙, this means the present secondary could be transferred and/or lost 77% of its original mass and only its core is left.     

Observations of active-chromosphere stars – V. A photometric study of the RS CVn system CF Tuc (HD 5303)

The Wilson–Devinney program is used to model 27 light curves (our own and others) for CF Tuc. We find new parameters for the binary system, and estimate the longitudes and radii of the spots on the cooler secondary star. We also find a strong tendency for spots on the cooler star to appear in a limited range of longitudes, rather than to migrate fairly rapidly as for other RS CVn systems. There is evidence that the mean light level of the cooler star is varying cyclically.
The orbital period clearly changes discontinuously. We discuss this, and the apparently cyclic variations in mean light level, in relation to the model proposed by Applegate.     

A study of the photometric system of the Kiev network telescope

We performed a series of CCD observations in BVRI bands of a celestial region in cluster M67 (NGC 2682) to study the photometric system of the Kyiv network telescope. The signal recording system consists of a CGE-1400 telescope, Celestron #94175 focal reducer, an automatic turret with a set of UBVRI filters, and a Rolera Mgi CCD camera. The operating field of the system is 10.62′ × 10.62′. CCD images are processed in the MIDAS/ROMAFOT package. The reduction coefficients of the instrumental photometric system relative to Johnson’s BVRI system are determined. The resulted value of the module of distance to cluster M67 V ? M _V = 9.63 ^m does not contradict the results of other researchers. The mean square errors for one determination of stellar magnitude for different bands are 0.02–0.12 ^m . The errors in determining equatorial coordinates in the TYCHO-2 catalog system are ± 1″.     

A long-term UBVRI photometric study of the pre-main sequence star V350 Cep

Results from UBVRI optical photometric observations of the pre-main sequence star V350 Cep during the period 2004-2014 are presented.The star was discovered in 1977 due to its remarkable increase in brightness by more than 5 mag(R).In previous studies,V350 Cep was considered to be a potential FUor or EXor eruptive variable.Our data suggest that during the period of observations the star maintains its maximum brightness with low amplitude photometric variations.Our conclusion is that V350 Cep was probably an intermediate object between FUors and EXors,similar to V1647 0ri.     

A photometric study of the contact binaries V523 Cas and TY UMa

Broad-band V and I photometry of the short-period W UMa-type contact binaries V523 Cas and TY UMa are reported. From the light curves, the system parameters have been determined and evidence is presented for extensive spot activity in both systems, with V523 Cas being the more active system. A compilation of all the available photoelectric and CCD-based timings of eclipse minima is made; the O–C diagrams show evidence for an increasing period in the case of V523 Cas and a decreasing period in TY UMa. In addition we derive a more accurate astrometric position for V523 Cas from our CCD images.     

A simultaneous spectroscopic and photometric study of two eclipsing binaries: V566 Oph and V972 Her

In this study, we have performed simultaneous solutions of light and radial velocity curves of two eclipsing binary systems, V566 Oph and V972 Her. We observed both systems spectroscopically with a very recently installed spectrograph on the 40 cm telescope, T40, located in Ankara University Kreiken Observatory (AUKR), for the first time. We made use of the photometric data from the Hipparcos satellite for V972 Her, while we obtained the photometric observations of V566 Oph by using the 35 cm telescope, T35, located also in our observatory campus. We derived the absolute parameters for both systems and discussed their evolutionary states. In addition to the simultaneous analysis, we have also analyzed the change in mid-eclipse times for V566 Oph, and found cyclic variations, for which we have discussed light-time effect and magnetic activity as their potential origin, superimposed on a secular change due to a mass transfer between the components of the binary.     

Improved photometric elements for the eclipsing system V1016 Ori

Published observations of the times of individual minima are analyzed by a least squares technique to determine O-C as a function of orbit number for the eclipsing system V1016 Ori. The following photometric elements are found: MinI=JD2441966.831(4)+65.43284(5)E.     

A 2007 photometric study and UV spectral analysis of the Wolf‐Rayet binary V444 Cyg

Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied. The Wilson‐Devinney (WD) analysis, using new BV observations carried out at the Ankara University Observatory, revealed the masses, radii, and temperatures of the components of the system as M_WR = 10.64 M_⊙, M_O = 24.68 M_⊙, R_WR = 7.19 R_⊙, R_O = 6.85 R_⊙, T_WR = 31 000 K, and T_O = 40000 K, respectively. It was found that both components had a full spherical geometry, whereas the circumstellar envelope of the WR component had an asymmetric structure. The O – C analysis of the system revealed a period lengthening of 0.139 ± 0.018 syr^–1, implying a mass loss rate of (6.76 ± 0.39) ×10^–6 M_⊙ yr^–1 for the WR component. Moreover, 106 IUE‐NEWSIPS spectra were obtained from NASA's IUE archive for line identification and determination of line profile variability with phase, wind velocities and variability in continuum fluxes. The integrated continuum flux level (between 1200–2000 Å) showed a mild and regular increase from orbital phase 0.00 up to 0.50 and then a decrease in the same way back to phase 0.00. This is evaluated as the O component making a constant and regular contribution to the system's UV light as the dominant source. The C IV line, originating in the circumstellar envelope, had the highest velocity while N IV line, originating in deeper layers of the envelope, had the lowest velocity. The average radial velocity calculated by using the C IV line (wind velocity) was found as 2326 km s^–1 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A detailed study of Cepheid photometric properties in the Walraven system

We have used the extensive set of photometric data in the VBLUW system (Pel, 1976) to perform a thorough statistical analysis of the physical properties of Cepheid variables, which can be inferred directly from these data. We have dealt with the problem of determining colour excesses and mean colours and temperatures; theoretical masses, radii and luminosities have been recalculated.