A dynamical solution of the triple asteroid system (45) Eugenia

We present the first dynamical solution of the triple asteroid system (45) Eugenia and its two moons Petit–Prince (diameter ∼ 7 km) and S/2004 (45) 1 (diameter ∼ 5 km). The two moons orbit at 1165 and 610 km from the primary, describing an almost-circular orbit (e ∼ 6 × 10⁻³ and e ∼ 7 × 10⁻² respectively). The system is quite different from the other known triple systems in the main belt since the inclinations of the moon orbits are sizeable (9° and 18° with respect to the equator of the primary respectively). No resonances, neither secular nor due to Lidov–Kozai mechanism, were detected in our dynamical solution, suggesting that these inclinations are not due to excitation modes between the primary and the moons. A 10-year evolution study shows that the orbits are slightly affected by perturbations from the Sun, and to a lesser extent by mutual interactions between the moons. The estimated J₂ of the primary is three times lower than the theoretical one, calculated assuming the shape of the primary and an homogeneous interior, possibly suggesting the importance of other gravitational harmonics.     

AV Hydrae: A Near-Contact Semi-Detached Binary with Possible Massand Angular Momentum Loss

The photoelectric observations of the neglected binary AV Hya published by Srivastava and Kandpal (1980) have been re-analyzed using Wilson-Devinney's synthetic light-curve program. The binary turns out to be a near-contact semi-detached system. The primary, more massive, more luminous and greater component, eclipsed at primary minimum, is detached from its Roche lobe (85%). The secondary fills its Roche lobe and has a temperature difference of T=,-3414 K. As with other semi-detached binaries, the secondary is more evolved than that of the primary. Thetimes of light minima of the eclipsing have been analyzed,showing that the orbital period of AV Hya undergoes acontinuous decrease with a rate of dP/dE=-8.26×10^-8 day/year. The mass transfer between the twocomponents can not explain the present orbital period variationsince the secondary component is filling the Roche lobe. Theorbital period change demonstrates that the system may undergoa secular mass and angular momentum loss and the system mayevolve from the present short-period near-contact system intoan A-type contact binary.     

The almost contact system RU Eridani

TheV andB light curves of the eclipsing binary RU Eridani, published by Sarma and Sanwal (1981), have been analysed by means of the Wilson and Devinney (1971) method, in order to obtain a solution based on the Roche model, as distinct from the Russell and Merrill model, used by Sarma and Sanwal. The system turns out to consist of an evolved K1 secondary which appears to fill the lobe, capable of containing its mass, and of an F0 V primary, which seems almost to fill its own. An estimate of the absolute elements of RU Eri has been made, on the assumption that the primary has a mass corresponding to its spectral type according to Allen (1973).     

New observations,photometric study and preliminary elements of the W UMa system DF CVn

CCD (V) light curve of the EW‐type eclipsing variable DF CVn was obtained during seven nights in April–May, 2004. With our data we were able to determine 4 new times of minimum light. The light curve appears to exhibit a typical O'Connell effect, with Maximum I brighter than Maximum II by 0.013 mag. in V. TwoWilson‐Devinney (WD) code working sessions, using the V light curve, were done with and without spots. The analysis of the results shows that the best fit was obtained with the spotted solution and indicates contact geometry. The photometric mass ratio of the system is found to be q = 0.347 and its inclination i = 72°, the primary minimum shows a transit. The star may be classified as an A‐type W Uma system. Assuming a reasonable value for the mass of the primary component an estimate of the absolute elements of DF CVn has been made, with the assumption that the primary has a mass corresponding to its spectral type according to Straizys and Kuriliene (1981). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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)     

Revised photometric elements of three semi-detached binary systems

TheV andB light curves of three Algol-type eclipsing binaries (UZ Cyg, VW Cyg, AQ Peg), observed by Ammanet al. (1979), have been analysed using the Wilson and Devinney (1971) model. We find that all of them are semi-detached systems, with A-type primary components and K-type evolved secondary which fill the corresponding lobe, although VW Cyg should perhaps be considered as an sd-d system.     

Spectral-luminosity classification,colour variations and suspected beta canis Majoris-type variability in IZ Persei

The colour indices and the spectrum-luminosity classification of the eclipsing binary system IZ Persei have been presented for the first time. The colour indices of the system appear reddened. Applying the interstellar reddening corrections, the spectral-luminosity classes of the primary and the secondary components of IZ Per come out to be B2.5III-V and B5III-V, respectively. The averageB-V andU-B colour excesses come out to be 0 ^m .4 and 0 ^m .2, respectively. The colour indices show continuous variation throughout the cycle, and indicate the presence of intrinsic variability. Tentative analysis suggests that the primary component of IZ Per is a Beta Canis Majoris-type variable. The possibility of a shell has also been discussed.     

Three-colours photoelectric observations of W UMA-system BB Pegasi

The paper givesUBV photoelectric light curves of the eclipsing binary BB Peg obtained in one of the nights in August 1982 and four nights of November 1984. A comparison has been made with previous light curves of this binary system. Two salient points arise from the light curves, (i) the depth of the primary eclipse could be variable, (ii) the period of the system has probably been increased.     

Equilibrium Structures of Differentially Rotating and Tidally Distorted White Dwarf Models of Stars

In this paper we present a method for computing the equilibrium structures and various physical parameters of a primary component of the binary system assuming that the primary is more massive than the secondary and is rotating differentially according to the law of the w² = b₀ + b₁ × s² + b₂ × s⁴, w being the angular velocity of rotation of a fluid element distant s from the axis of rotation and b₀, b₁, b₂ suitably chosen numerical constants. This method utilizes the averaging approach of Kippenhahn and Thomas (1997) and the concept of Roche equipotentials in a manner earlier used by Mohan et al. (1997) to incorporate the effects of rotation and tidal distortions on the equilibrium structures of certain rotationally and tidally distorted stellar models. The use of the method has been illustrated by applying it to obtain the structures and some observable parameters of certain differentially rotating and tidally distorted binary systems whose primary component is assumed to be a white dwarf star.     

V758 Centauri:UBV photometry

The W UMa system V758 Centauri has been observed photoelectrically in theUBV system at Bosque Alegre Station, and the comparison and check stars at Cerro Tololo Observatory. Full light curves were constructed from 1043 differentialUBV observations. A study of 11 photoelectric times of minimum light and of earlier photographic data shows that the period remained constant in the last century, V758 Cen shows a total occultation at secondary minimum, thus being an A-type W UMa system. Asymmetries are observed at primary minima whereas maxima are of different heights. Thermal decoupling of the components is suggested by the depth ratio of the minima; V758 Cen may be at the broken phase (or marginal contact) of a thermal relaxation oscillation.     

V2213 Cyg is a New W Uma-Type System

V2213 Cyg was discovered as a variable star by Pavlenko (1999) in 1998. We present our photometry of V2213 Cyg from 1998–2003 based on CCD observations with the K-380 Cassegrain telescope of CrAO and the 60 cm Zeiss telescope of SAI. Observations have been carried out mostly in R and sometimes in B and V Johnson system. The total amount of data is 2270 points, covering ∼50 nights. We classify this binary as a W UMa-type contact system. Using all data we determined the orbital period to be 0.350079 ± 0.000007 day. The mean brightness varies between R = 14.35 and 14.05. The mean 1999–2003 orbital light curve has two humps and a primary minimum (I), which is 0.04 mag brighter than the deeper secondary one (II). The mean humps have slightly different height. The difference between two individual maxima varies within 0.1 mag, which may indicate an activity of the components. The highest hump is an asymmetrical one: it has sort of a shoulder at phases 0.75–0.80, before entering the less deep primary minimum (phase 0.0). The system is rather reddened, its colour indices are: B−V ∼ 0.8 and V−R ∼ 0.7, and give a spectral class of V2213 Cyg earlier than K.     

UBV photometry of DX Aquarii

U, B, V photometry of the eclipsing binary DX Aqr has been presented for the first time. The period of the system comes out to be nearly half the period given by Strohmeier (1966) and a value of O^d.472502 has been determined. The colour of the system has been discussed. The primary eclipse is a total occulation. The orbit seems to be eccentric. The system belongs to Algol type. DX Aqr may be a very complicated system. The present results are considerably different from those of earlier investigations.     

Modeling the Eclipsing Binary System VW Cygni

Five color UBVRI photometric and polarimetric measurements of the eclipsing binary VW Cyg are reported. It is shown that in the primary minimum the luminosity is attenuated (at short wavelengths) even after passage of the second contact. This fact is interpreted as evidence of gaseous structures in the system. The exchange of matter among the system components is also confirmed by the O-C curve constructed from data covering nearly a hundred years. Polarimetric analysis makes it possible to isolate the intrinsic (P=0.030±0.02) and interstellar components of the polarization. The UBVRI light curves of VW Cyg have been resolved. This was done using an algorithm for synthesizing theoretical light curves in the Roche model. Good agreement was obtained between the theoretical curves and observations in the V, R, and I bands, but the observed minimum depths in the U and B bands exceed the theoretical values. This appears to be caused by gas flows in the system.     

EB-type contact binary do cas with a large temperature difference

NewUBV photoelectric observations of EB-type contact binary DO Cas were made on 4 nights from February 1986 to February 1987. The obtained light curves in combination with the radial-velocity curve of the primary published by Mannino (1958) of DO Cas have been solved simultaneously using the Wilson-Devinney synthesis code. The system is found to be a contact binary with a degree of overcontact of 14%. It may be concluded that DO Cas is an evolved contact binary.     

Synthetic light curve solutions for the W UMa-system BV draconis

Synthetic light curve solutions for the W UMa-system BV Dra have been determined by applying the Wilson and Devinney approach toUBV-observations of 1979–1980 andBV-observations of 1976. All solutions are very similar and correspond to a system with an overcontact configuration and an A-type light curve. A reasonable solution results from the assumption of a G1V spectral type for the primary component. Solutions with a F7V spectral type for the primary component are also presented. The photometric mass ratios are close to the spectroscopic values.     

Das System des Bedeckungssterns TT Lyrae

For this typical Algol system with the period 5.24 days, complete light curves in two colours have been derived from 160 photoelectric measurements in B and 173 in V. The primary minimum has been found to be total and asymmetric. To get a satisfactory photometric solution it was necessary to allow for the dissimilarity of the components. For the coefficients of limbdarkening of the Ao-component the values x = 0.35 · 0.11 (B) and 0.44 · 0.10 (V) have been deduced.     

Radial velocity and light curves analysis of the eclipsing binary NN Vir

The eclipsing binary NN Vir is a short period system showing an EW‐type light curve. Photometric observations of NN Vir were done by Gomez‐Ferrellad & Garcia‐Melendo (1997) at Esteve Duran Observatory. We used photometric data of NN Vir for light curve analysis. The available spectroscopic data of NN Vir is new and we also used the first radial velocity data of this system obtained by Rusinski & Lu (1999) for analysis. The radial velocity and light curves analysis was made with the latest version ofWilson program(1998) and the geometric and physical elements of the system are derived. By searching the simultaneous solutions of the system, we have determined the masses and radii of the components : 1.89(M_⊙) and 1.65(R_⊙) for the primary component; 0.93(M_⊙) and 1.23(R_⊙) for the secondary component. We estimated effective temperatures of 7030(K) for the primary and 6977(K) for the secondary component. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determining the orientation parameters of the ICRS/UCAC2 system using the Kharkov catalog of absolute stellar proper motions

The absolute proper motions of about 275 million stars from the Kharkov XPM catalog have been obtained by comparing their positions in the 2MASS and USNO-A2.0 catalogs with an epoch difference of about 45 yr for northern-hemisphere stars and about 17 yr for southern-hemisphere stars. The zero point of the system of absolute proper motions has been determined using 1.45 million galaxies. The equatorial components of the residual rotation vector of the ICRS/UCAC2 coordinate system relative to the system of extragalactic sources have been determined by comparing the XPM and UCAC2 stellar proper motions: ω _x,y,z = (−0.06, 0.17, −0.84) ± (0.15, 0.14, 0.14) mas yr⁻¹. These parameters have been calculated using about 1 million faintest UCAC2 stars with magnitudes R _UCAC2 > 16 ^m and J > 14 ^m . 7, for which the color and magnitude equation effects are negligible.     

Geoidal potential free of zero-frequency tidal distortion

It has been proved that the geoidal valueW ₀ is not dependent on the system used for defining the geoid surface. It is the same for the zero-frequency tidal system, mean system and tide-free system. It has been suggested,W ₀ be adopted as primary constant defining the length dimensions of celestial bodies.     

Equilibrium Structures of Differentially Rotating Primary Components of Binary Stars

In this paper a method is proposed for computing the equilibrium structures and various other observable physical parameters of the primary components of stars in binary systems assuming that the primary is more massive than the secondary and is rotating differentially about its axis. Kippenhahn and Thomas averaging approach (1970) is used in a manner earlier used by Mohan, Saxena and Agarwal (1990) to incorporate the rotational and tidal effects in the equations of stellar structure. Explicit expressions for the distortional terms appearing in the stellar structure equations have been obtained by assuming a general law of differential rotation of the typeω² = b ₀+b ₁ s ²+b ₂ s ⁴, where ω is the angular velocity of rotation of a fluid element in the star at a distance s from the axis of rotation, and b ₀, b ₁, b ₂ are suitably chosen numerical constants. The expressions incorporate the effects of differential rotation and tidal distortions up to second order terms. The use of the proposed method has been illustrated by applying it to obtain the structures and observable parameters of certain differentially rotating primary components of the binary stars assuming the primary components to have polytropic structures. This revised version was published online in July 2006 with corrections to the Cover Date.