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Register a new userPhotometric Investigation of the Contact Binary GU Ori with High Metallicity
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GU Ori was observed with the 1m telescope at Yunnan Observatories in 2005. To determine its physical properties, the Wilson-Devinney program is used. The results reveal that GU Ori is a W-subtype shallow contact binary with a more massive but cooler star 2. The mass of its two component stars are estimated to be $M_1 = 0.45M_odot$, $M_2 = 1.05M_odot$. The OConnell effect was reported to be negative on the light curves observed in 2005. However, it changed to a positive one on the light curves observed from 2011 to 2012. The mean surface temperatures of star 2 ($T_2$) determined by the two sets of light curves were different, which may result from stellar activities. The O - C diagram shows that the period of GU Ori is decreasing at a rate of $dP/dt=-6.24times{10^{-8}}daycdot year^{-1}$, which may be caused by mass transfer from star 2 to star 1 with a rate of $frac{dM_{2}}{dt}= - 2.98times{10^{-8}}M_odot/year$. GU Ori is a contact binary with quite high metallicity.
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Multi-color light curves of V1197 Her were obtained with the 2.4 meter optical telescope at Thai National Observatory and the Wilson-Devinney (W-D) program is used to model the observational light curves. The photometric solutions reveal that V1197 Her is a W-subtype shallow contact binary system with a mass ratio of $q = 2.61 $ and fill-out factor to be $f = 15.7,%$. The temperature difference between the primary star and secondary star is only $140K$ in spite of the low degree of contact, which means that V1197 Her is not only in geometrical contact configuration but also already under thermal contact status. The orbital inclination of V1197 Her is as high as $i = 82.7^{circ}$, and the primary star is completely eclipsed at the primary minimum. The totally eclipsing characteristic implies that the determined physical parameters are highly reliable. The masses, radii and luminosities of the primary star (star 1) and secondary star (star 2) are estimated to be $M_{1} = 0.30(1)M_odot$, $M_{2} = 0.77(2)M_odot$, $R_{1} = 0.54(1)R_odot$, $R_{2} = 0.83(1)R_odot$, $L_{1} = 0.18(1)L_odot$ and $L_{2} = 0.38(1)L_odot$. The evolutionary status of the two component stars are drawn in the H - R diagram, which shows that the less massive but hotter primary star is more evolved than the secondary star. The period of V1197 Her is decreasing continuously at a rate of $dP/dt=-2.58times{10^{-7}}daycdot year^{-1}$, which can be explained by mass transfer from the more massive star to the less massive one with a rate of $frac{dM_{2}}{dt}=- 1.61times{10^{-7}}M_odot/year$. The light curves of V1197 Her is reported to have the OConnell effect. Thus, a cool spot is added to the massive star to model the asymmetry on light curves.
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.
We present the results of the study of the contact binary system BO CVn. We have obtained physical parameters of the components based on combined analysis of new, multi-color light curves and spectroscopic mass ratio. This is the first time the latter has been determined for this object. We derived the contact configuration for the system with a very high filling factor of about 88 percent. We were able to reproduce the observed light curve, namely the flat bottom of the secondary minimum, only if a third light has been added into the list of free parameters. The resulting third light contribution is significant, about 20-24 percent, while the absolute parameters of components are: M1=1.16, M2=0.39, R1=1.62 and R2=1.00 (in solar units). The O-C diagram shows an upward parabola which, under the conservative mass transfer assumption, would correspond to a mass transfer rate of dM/dt = 6.3 times 10-8Modot/yr, matter being transferred from the less massive component to the more massive one. No cyclic, short-period variations have been found in the O-C diagram (but longer-term variations remain a possibility)
The first photometric analysis of V811 Cep was carried out. The first complete light curves of V, R and I bands are given. The analysis was carried out by Wilson-Devinney (W-D) program, and the results show that V811 Cep is a median-contact binary ($f=33.9(pm4.9)%$) with a mass ratio of 0.285. It is a W-subtype contact binary, that is, the component with less mass is hotter than the component with more mass, and the light curves are asymmetric (OConnell effect), which can be explained by the existence of a hot spot on the component with less mass. The orbital inclination is $i=88.3^{circ}$, indicating that it is a totally eclipsing binary, so the parameters obtained are reliable. Through the O-C analyzing, it is found that the orbital period decreases at the rate of $dot{P}=-3.90(pm0.06)times 10^{-7}d cdot yr^{-1}$, which indicates that the mass transfer occurs from the more massive component to the less massive one.
Two sets of light curves in $V$ $R_c$ $I_c$ bands for a newly discovered binary system UCAC4 436-062932 are obtained and analyzed using the Wilson-Devinney (W-D) code. The two sets of light curves get almost consistent results. The determined mass ratio is about $q = 2.7$ and the less massive component is nearly $250K$ hotter than the more massive one. The solutions conclude that UCAC4 436-062932 is a W-subtype shallow contact (with a contact degree of $f = 20,%$) binary system. Since the OConnell effect appears on one set of the light curves, theories proposed to explain the effect are discussed. We assume that spot model may be the more plausible one to the OConnell effect appeared on the asymmetric light curves of the binary system UCAC4 436-062932. Therefore, we add a cool spot on the surface of the more massive star (component with lower effective temperature) and get a quite approving results for the light curve fitting. It will provide evidence to support the spot model in the explanatory mechanism of OConnell effect.
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