DEEP, LOW MASS RATIO OVERCONTACT BINARY SYSTEMS. IX. V345 GEMINORUM WITH A BRIGHT VISUAL PAIR

Abstract

CCD photometric observations of the visual binary, V345 Geminorum, obtained from 2007 January 24 to 2009 March 22, are presented. When comparing the light curves in 2007 and 2008, it is found that there appears to be an O'Connell effect in the light curves of 2008. From those observations, two sets of photometric solutions were deduced using the 2003 version of the W-D program. The results indicated that V345 Gem is a low mass ratio overcontact binary with f = 72.9%(+/- 3.1%). The asymmetric light curves in 2008 may be attributed to the activity of starspot, whose area is up to 1.55% of the area of the more massive component. The contributions of the third light to the total light are approximately 20% in the BVR bands. The absolute physical parameters for V345 Gem were obtained first. From the log L-log M diagram of the binary-star evolution, the primary component is an evolved star. From the O-C curve for V345 Gem, it is discovered that there exists a long-term period increase with a cyclic variation. The period and amplitude of the cyclic variation are P(3) = 646.7(+/- 0.7) day and A = 0(d).0019(+/- 0(d).0002), which may be caused by the light-time effect via the assumed third body. If it is true, the visual binary V345 Gem may be a quadruple star. The kind of additional component may remove angular momentum from the central system, which may play an important role for the formation and evolution of the binary. The secular period increases at a rate of dP/dt = +5.88 x 10(-8) d yr(-1), indicating that the mass transfers from the less massive component to the more massive component. With mass transferring, the orbital angular momentum decreases while the spin angular momentum increases. When J(spin)/J(orb) > 1/3, this kind of deep, low mass ratio overcontact binary with secular period increase may evolve into a rapid-rotating single star.