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Register a new userCCD photometric study of the W UMa-type binary II CMa in the field of Berkeley 33
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The CCD photometric data of the EW-type binary, II CMa, which is a contact star in the field of the middle-aged open cluster Berkeley 33, are presented. The complete R light curve was obtained. In the present paper, using the five CCD epochs of light minimum (three of them are calculated from Mazur et al. (1993)s data and two from our new data), the orbital period P was revised to 0.22919704 days. The complete R light curve was analyzed by using the 2003 version of W-D (Wilson-Devinney) program. It is found that this is a contact system with a mass ratio $q=0.9$ and a contact factor $f=4.1%$. The high mass ratio ($q=0.9$) and the low contact factor ($f=4.1%$) indicate that the system just evolved into the marginal contact stage.
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The first four-color light curves of V868 Mon in the $B$ $V$ $R_c$ and $I_c$ bands are presented and analyzed by using the Wilson-Devinney method of the 2013 version. It is discovered that V868 Mon is an A-subtype contact binary (f=$58.9,%$) with a large temperature difference of 916$K$ between the two components. Using the eight new times of light minimum determined by the authors together with those collected from literatures, the authors found that the general trend of the observed-calculate ($O$-$C$) curve shows a upward parabolic variation that corresponds to a long-term increase in the orbital period at a rate of $dP/dt=9.38times{10^{-7}}daycdot year^{-1}$. The continuous increase may be caused by a mass transfer from the less massive component to the more massive one.
The $B$ $V$ $R_c$ $I_c$ bands light curves of the newly discovered binary system astrobj{GSC 03122-02426} are obtained and analyzed using the Wilson-Devinney (W-D) code. The solutions suggest that the mass ratio of the binary system is $q = 2.70$ and the less massive component is $422K$ hotter than the more massive one. We conclude that astrobj{GSC 03122-02426} is a W-subtype shallow contact (with a contact degree of $f = 15.3,%$) binary system. It may be a newly formed contact binary system which is just under geometrical contact and will evolve to be a thermal contact binary system. The high orbital inclination ($i = 81.6^{circ}$) implies that astrobj{GSC 03122-02426} is a total eclipsing binary system and the photometric parameters obtained by us are quite reliable. We also estimate the absolute physical parameters of the two components in astrobj{GSC 03122-02426}, which will provide fundamental information for the research of contact binary systems. The formation and evolutionary scenario of astrobj{GSC 03122-02426} is discussed.
Using multicolour photometry we have confirmed the binary nature of the new W-type W UMa eclipsing binary VSX J053024.8+842243 and established its primary eclipse ephemeris to be HJD = 2455924.38150(26) + 0.4322929(1) * E. Using the light curve modelling code PHOEBE and published data on the evolution of W-type contact binaries we found the primary and secondary components to have masses 0.50 Msun and 1.44 Msun, radii 0.87 Rsun and 1.42 Rsun, luminosities 0.98 Lsun and 1.91 Lsun, temperatures 6145 K and 5702 K and binary orbit inclination 59.4{deg}. We found the distance to the binary to be 511 parsec, its E(B-V) colour excess 0.04 and its intrinsic (B-V) colour index 0.62. A low resolution spectrum corrected for interstellar reddening confirmed its spectral type as G2V.
This study is an attempt to determine the metallicities of WUMa-type binary stars using spectroscopy. ~4,500 spectra collected at the David Dunlap Observatory were subject to the same Broadening Function processing to determine the combined line strength in the spectral window centered on the MgI triplet (5080-5285A). Individual integrated BFs were phase averaged to derive a single line-strength indicator. The sample was limited to 90 EW binaries with the strict phase-constancy of colors and without spectral contamination by companions. The best defined results were obtained for a F-type sub-sample (0.32<(B-V)0<0.62) of 52 stars for which the BF strengths could be interpolated in the model predictions. The metallicities, [M/H], for the F-type sub-sample indicate abundances roughly similar to the solar [M/H], but with a large scatter which is partly due to combined random and systematic errors. Because of a color trend resulting from limitations in our approach, we set the scale of metallicities to correspond to that derived from the m_1 index of the Stromgren photometry for F-type binaries. The trend-adjusted [M/H]1 are distributed within -0.65<[M/H]1<+0.50, with the spread reflecting genuine metallicity differences between stars. One half of the F-sub-sample binaries have [M/H]1 within -0.37<[M/H]1 +0.10, a median of -0.04 and a mean of -0.10, with a tail towards low metallicities, and a possible bias against very high metallicities. A parallel study of kinematic data, utilizing the most reliable and recently obtained proper motion and radial velocity data for 78 stars of the full sample, shows that the F-type sub-sample binaries have similar kinematic properties to solar neighborhood, thin-disk dwarfs with ages about 3 - 5.5 Gyr. The F-type binaries which appear to be older than the rest tend to have systematically smaller mass-ratios than most of the EW binaries of the same period.
ROTSE1 J164341.65+251748.1 was photometrically observed in the V band during three epochs with the 0.84-m telescope of the San Pedro Martir Observatory in Mexico. Based on additional BVR photometry, we find that the primary star has a spectral type around G0V. The light curve of the system is typical of a W~UMa type binary stars and has an orbital period of $sim$ 0.323 days. In an effort to gain a better understanding of the binary system and determine its physical properties, we analyzed the light curve with the Wilson and Devinney method. We found that ROTSE1 J164341.65+251748.1 has a mass ratio of $sim$ 0.34 and that the less massive component is over 230 K hotter than the primary star. The inclination of the system is $sim$ 84.6 degrees, and the {bf degree} of over-contact is 11%. The analysis shows the presence of variable bright spots on the primary star.
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