Photometric membership and metallicities of red giant candidates in selected open clusters

As part of a long‐term project to determine abundances and astrophysical properties of evolved red stars in open clusters, we present high‐precision DDO photoelectric observations for a sample of 33 red giant candidates projected in the fields of nine Galactic open clusters. These data are supplemented with UBV photoelectric photometry of 24 of these stars as well as with CORAVEL radial‐velocity observations for 13 red giant candidates in four of the clusters. We also present Washington photoelectric photometry of a small sample of red giant candidates of the open cluster Ruprecht 97. The likelihood of cluster membership for each star photometrically observed and for 23 additional red giant candidates with UBV and DDO data available in the literature, is evaluated by using two independent photometric criteria. Nearly 82% of the analysed stars are found to have a high probability of being cluster giants. Photometric membership probabilities show very good agreement with those obtained from CORAVEL radial velocities. While E (B –V) colour excesses were determined from combined B – V and DDO colours, calibrations of the DDO system were used to derive MK spectral types, effective temperatures and metallicities. The derived DDO metallicities range between values typical of moderately metal‐poor clusters ([Fe/H] = –0.19) to moderately metal‐rich ([Fe/H] = 0.25) ones. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoelectric study of AW UMa

UBV photoelectric photometry of the eclipsing binary system AW UMa has been presented. A slightly improved period of 0 _. ^d 4387304 has been given. The colour of the system has been discussed. Eccentricity is present in the system. Light and colour curves show that intrinsic light variations may be present in the system. The presence of mass transfer is a possibility.     

Two UBV sequences,north and south of the galactic cluster NGC 5823

Photoelectric UBV observations of 69 stars, distributed in two sequences north and south of the galactic star cluster NGC 5823, are reported.     

New times of the minima and light elements of SW Lacertae

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.     

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.     

Photometrische Untersuchungen im Zentralgebiet der Praesepe (NGC 2632)

In supplementing the photometric sequence in the central part of the Praesepe cluster and its extension to fainter stars a photographic photometry in UBV on plates of the 134/200/400 cm – Schmidt telescope of Karl-Schwarzschild-Observatory was done. The already known photometric data from stars obtained by HAFFNER , HECKMANN and WEIS were completed by (U – B) colours on the base of JOHNSON'S photoelectric photometry. Besides, a number of brighter and fainter stars, cluster members, white dwarfs inclusively and field stars were investigated to set up a photometric sequence down to V ≈ 18.^m9. A finding chart where all the measured stars are marked is given.     

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.     

Absolute energy distribution in spectra of V 2291 Ophiuchi: The eclipse of 1990

The results of broadband photoelectric observations of V 2291 Oph between 1990 and 1992 have been considered and unified to produce composite UBV light curves. The spectral types of the binary companions and their luminosities are estimated using the absolute spectrophotometry of V 2291 Oph.     

UBV observation and analysis of VV Orionis

TheUBV photoelectric observation of the eclipsing binary star VV Ori were made at Al-Battani Observatory, Baghdad, Iraq, during nine nights in November and December, 1984 and January, 1985. As a result, three light curves were completed.An analysis of theB andV normal points light curves using the optimization method shows the existence of a slight shift in the primary mid-minimum epoch and the temperature of the secondary component is consistent with B5-type star. A new set of geometrical and physical elements is also presented.     

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.     

Photometric observations of NY Cephei

NewUBV photoelectric observations of NY Cep were made from 1982 to 1989 with GOTO 61-cm telescope at the Yonsei University Observatory. Seven times of minimum light were obtained. An improved orbital period of 15.27566 day was determined. The light curves were analyzed using the Wilson-Devinney method. It is confirmed that NY Cep is a detached system and the absolute dimensions are also obtained. It is found that the secondary eclipse does not occur due to large eccentricity and inclination.     

UBV photometry of clusters in M31

A critical review is given of all published photoelectricUBV photometry of star clusters in the Andromeda Nebula. Observations by Sharovet al. are shown to exhibit rather large random errors, but no systematic deviations from theUBV system.     

Photometry of the contact binary system V471 Cas

UBV photoelectric observations of the W UMa-type binary V471 Cas were made from September to November 1984. Its colour indices were found to be(B-V)=0 _. ^m 771±0 _. ^m 02 and(U-B)=0 _. ^m 196±0 _. ^m 02. TheU, B, andV light curves of V471 Cas show some photometric fluctuations. We found that its orbital period is not 0.335998 days which was given by GCVS (1986), but 0.405356 days.Photometric orbital elements of V471 Cas were found using the Wilson-Devinney method. V471 Cas is a contact system, in which the overcontact factor is 0.19, its mass ratio of two components is 0.5947, and orbital minclination is in 83.29 degrees.     

Photoelectric catalogue of globular clusters in the Andromeda Nebula M31 and its companions NGC 147, NGC 185, and NGC 205

The photoelectric catalogue of the globular clusters (including the objects previously considered to be clusters) in the Andromeda Nebula M31 and its companions NGC 147, NGC185, and NGC 205 is presented. The catalogue based on all published data includes 338 objects withUBV, six objects withBV, and one object withV measurements.     

Orbital period variation of the eclipsing binary system TT Herculis

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)     

Age determination of the open cluster NGC 2287 (M41)

We have estimated the age of the open cluster NGC 2287 (M41) by taking into account the rotation of the member stars.TheUBV photoelectric measurement values were taken from Eggen (1974). Besides the Main-Sequence stars this cluster has seven red giants, all of them above the turn-off point.Having obtained the theoretical Hertzsprung-Russell diagram from observed colour-magnitude diagram, we have discussed two methods, given in the literature, to estimate the age of the cluster under consideration. The first method we have followed is to determine the turn-off point on the cluster Main-Sequence. The other is fitting the position of the red giants with the evolutionary tracks of rotating stars with different masses on the Hertzsprung-Russell diagram.We have estimated the cluster age based on the turn-off point as 3.10×10⁷ yr. From the fitting of the evolutionary tracks of rotating stars to the cluster Hertzsprung-Russell diagram, we infer that the age of the cluster is about 8.00×10⁷ yr.     

A new stellar standard sequence in the coma cluster of galaxies. (preliminary report)

Photographic magnitudes in the UBV system of 39 stars in the Coma cluster of galaxies are given.     

Preliminary Analysis of Photometric Variations of the Central Star of the Planetary Nebula Sh 2-71

We confirm the presence of regular UBV(RI)_C light variations of the object in the center of the planetary nebula Sh 2-71, with an improved period of P = 68.132 ± 0.005 days. The shapes and amplitudes of light curves, in particular colours, are briefly discussed.     

Disc system delta Capricorni

FirstUBV photoelectric photometry of the eclipsing binary system Cap has been presented. An improved period of 1^d.022766 has been given. The duration of primary eclipse comes out to be more than double the duration given earlier. The depth has also been found to have increased. The light changes during eclipses show slight asymmetry. Eccentricity appears to be present in the system. Light and colour curves show variations. Primary component appears to be surrounded by a disc, the size of which is comparable to the size of the primary component. Two dips are seen around phases 0.20 and 0.67, the first appears more definitive, and is attributed to the wave-like distortion, like the one found in RS CVn binaries. The discussion reveals that Cap is a very complicated system.     

Ubv(Ri)C Photometry of the Contact W Uma Binary Bd + 14∘5016

New UBV(RI)_C observations and radial velocities of the W UMa-type system BD + 14^∘5016 were collected. Changes of the properties of a hot spot, located on the surface of the primary component, have been noticed.