New Photometric Investigation of the Solar-Type Shallow-Contact Binary HH Bootis

The short-period solar-type contact binary HH Boo was monitored photometrically for about 8 years. It is found that the CCD light curves in the B, V, R, and I bands obtained in 2010 are symmetric, while the multicolor light curves observed in 2011 and 2012 by several investigators showed a positive O’Connell effect where the maxima following the primary minima are higher than the other ones. This indicates that the light curve of the solar-type contact binary is variable. By analyzing our multicolor light curves with the Wilson-Devinney code (W-D code), it is confirmed that HH Boo is a W-type shallow-contact binary system with a mass ratio of q = 1.703(31) and a degree of contact factor of f = 12.86%(0.73%). By including 109 new determined times of light minimum together with those compiled from the literature, it is detected that the O-C diagram shows a cyclic oscillation with a period of T3 = 6.58(11) yr and an amplitude of A3 = 0.0018(1) d. The cyclic change may reveal the presence of an extremely cool third body orbiting the central binary.

The Photometric Investigation of V921 Her Using the Lunar-Based Ultraviolet Telescope of Chang’e-3 Mission

The light curve of V921 Her in ultraviolet band observed by the Lunar-based Ultraviolet Telescope (LUT) is analyzed by the Wilson-Devinney code. Our solutions conclude that V921 Her is an early type marginal contact binary system with an additional close-in component. The binary system is under poor thermal contact with a temperature difference of nearly 700 K between the two components. The close-in component contributes about 19% of the total luminosity in the triple system. Combining the radial velocity study together with our photometric solutions, the mass of the primary star and secondary one is calculated to beM1=1.784 (±0.055)M⊙,M2=0.403 (±0.012)M⊙. The evolutionary scenario of V921 Her is discussed. All times of light minimum of V921 Her available in the bibliography are taken into account and theO-Ccurve is analyzed for the first time. The most probable fitting results are discussed in the paper, which also confirm the existence of a third component (P3=10.2year) around the binary system. The period of V921 Her is also undergoing a continuously rapid increase at a rate ofdP/dt=+2.79×10-7 day·year-1, which may be due to mass transfer from the less massive component to the more massive one.

CCD Photometric Study of the Puzzling W UMa-type Binary TZ Boo

The puzzling W-UMa type binary TZ Boo has been monitored at the University of Patras, Observatory from March to July 2010. Photometric solutions were determined through an analysis of the complete BVRI light curves with PHOEBE (Wilson-Devinney code) and published spectroscopic data. This low mass ratio binary turns out to be a deep overcontact system with f = 52.5% of A-subtype. A conservative spot model has been applied to fit the particular features of light curves. Based on our 7 new light minimum times and all others compiled from the literature over 70 years, we studied the orbital period from the O-C curve.