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Register a new userThe first four-color photometric investigation of the W UMa type contact binary V868 Mon
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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.
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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.
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 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.
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.
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.
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