PHOTOMETRIC STUDY AND PERIOD ANALYSIS OF THE CONTACT BINARY XZ LEONIS

• Published in: The Astronomical journal 2015-09, Vol.150 (3), p.1-8
• Main Authors: Luo, Chang Qing, Zhang, Xiao Bin, Deng, Licai, Wang, Kun, Luo, Yangping
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; binaries: close; binaries: eclipsing; Binary systems; CHARGE-COUPLED DEVICES; Contact; ECLIPSE; MASS TRANSFER; Mathematical models; Necks; Orbitals; OSCILLATIONS; PHOTOMETRY; RADIAL VELOCITY; RELAXATION; STAR EVOLUTION; STARS; stars: evolution; stars: individual (XZ Leo); Thermal relaxation
• ISSN: 0004-6256; 1538-3881; 1538-3881
• DOI: 10.1088/0004-6256/150/3/70

ABSTRACT We present multi-color CCD photometry of the neglected contact binary XZ Leo. Completely covered VRI band light curves and four times of minimum light were obtained. Combining the photometric and previously published radial-velocity data, a revised photometric analysis was carried out for the binary system by applying the Wilson-Devinney code. With a hot spot placed on the massive primary component near the neck region of the common envelope, the light curves were satisfactorily modeled. The photometric solution combined with the radial-velocity solution reveals that XZ Leo is an A-type contact binary with a degree of contact of 24( 1)%. The absolute parameters of the components were determined to be M1 = 1.74( 0.06)M , M2 = 0.61( 0.02)M , R1 = 1.69( 0.01)R , R2 = 1.07( 0.01)R , L1 = 6.73( 0.08) L , and L2 = 2.40( 0.04)L . Based on all the available data, the long-term orbital period behavior of the system was investigated. It indicates that the binary system was undergoing a continuous orbital period increase in the past three decades with a rate of , which suggests a probable mass transfer from the secondary to the primary component at a rate of . The binary system is expected to evolve into the broken-contact stage in years. This could be evidence supporting the thermal relaxation oscillation theory.