New light curve analysis and period changes of the overcontact binary XY Leonis

Abstract

Abstract. Light curves and photometric solutions of the contact binary XY Leo are presented. The UBVR light curves appear to be almost symmetric. The B and V light curves were analysed with the Wilson-Devinney code and the orbital parameters of the system were obtained and compared with those obtained in previous studies. All the times of minimum light were collected and combined with the new ones obtained in this study. The orbital period of the system oscillates with a period of 19.6 years and a semi-amplitude of 0.023 day. This regular change was analysed under the assumption of the third body hypothesis. The time delay and advance due to the orbit of the eclipsing pair around the third component were computed and subtracted from the original residuals obtained with the linear light elements. The remaining residuals also show a parabolic change. Therefore, we assumed that the orbital period of the system changes with time due to at least two different causes. The parabolic change of the period may be attributed to either mass transfer from less massive component to the more massive one, or an additional component bounded to the double binary system with a longer period.

Close binary and other variable stars in the solar-age Galactic open cluster M 67

“…Hence, a sinusoidal variation superimposed on an upward/downward parabola suggests mass transfer between the components of a binary system that has a third body orbiting it e.g. XY Leo (Yakut et al 2003), TY Boo (Yang et al 2007), V839 Oph (Akalin & Derman 1997), BB Peg (Kalomeni et al 2007). Usually, ephemeris of such a system is written as where the first two terms are linear, the third one is due to the period increase/decrease and the last term τ, is the light-time term, which was formalized by Irwin (1952) as…”

A Photometric Study of the Contact Binaries: XY Leo, EE Cet and AQ Psc

“…Hilditch 1981; Kaluzny & Pojmanski 1983;Hrivnak 1985) attributed to the asymmetric distribution of cool spot regions on one or both components. The orbital period of the system changes with time, and O-C residuals, indicating the differences between the observed times of eclipses and the calculated ones using the light elements, were studied by Gehlich, Prolss & Wehmeyer (1972), Kaluzny & Pojmanski (1983), Hrivnak (1985), Pan & Cao (1998) and recently by Yakut et al (2003). In the latter paper it was shown that the orbital period of the system oscillates with a period of 19.6 years, with a semi-amplitude of 0.023 days.…”

“…Also, Barden (1987) showed that a significant portion of the chromospheric emission observed by many investigators from XY Leo was, instead, associated with the components of the BY Dra binary, which together with XY Leo forms a quadruple system. Yakut et al (2003) analyzed the B and V light curves obtained during [2000][2001] with the 48 cm Cassegrain telescope at Ege University Observatory. They applied Wilson-Devinney code by assuming that there was a third light in the system.…”

“…Since the results of previous light curve analyses were available to us, in the present light-curve analysis the mass ratio of the components was fixed at the value q = m c /m h = 1.64, estimated by Yakut et al (2003) who used the semi-amplitudes of velocity curves derived by Barden (1987) from radial velocity studies. According to Yakut et al (2003), the temperature of the less-massive hotter component (eclipsed at I min ) was set at T h = 4850 K in agreement with the B -V colour of 0.82 and Popper (1980) calibration.…”

“…According to Yakut et al (2003), the temperature of the less-massive hotter component (eclipsed at I min ) was set at T h = 4850 K in agreement with the B -V colour of 0.82 and Popper (1980) calibration.…”