Period Change of W UMa Type Contact Binary AB And

• Main Authors: Ho Jin, Wonyong Han, Chun-Hwey Kim, Jae-Woo Lee, Woo-Baik Lee
• Format: Article
• Language: English
• Published: Korean Space Science Society (KSSS) 1997-12-01
• Series: Journal of Astronomy and Space Sciences
• Online Access: http://ocean.kisti.re.kr/downfile/volume/kosss/OJOOBS/1997/v14n2/OJOOBS_1997_v14n2_242.pdf

The CCD photometric observations of W UMa-type eclipsing binary AB And were made from September 1994 to October 1996. New four primary minimum times were obtained form these observations. The analysis of times of minimum light for AB And confirms other previous studies that the orbital period of AB And have been changing as a form of sinusoidal variation. In this paper, we calculated the new orbital elements with linear and nonlinear quadratic term, and the best fit equation is derived with the assumption that the period variation of AB And changes sinusoidal pattern. From the sinusoidal term of this orbital element, we calculate period variation as 92 years with amplitude of 0d.059. However this result considering only sinusoidal term was not satisfied with our recent observations. Thus, by assuming another parabolic period variation with the sinusoidal pattern, we derived the best fit orbital elements. From the quadratic coefficient of this orbital elements, we calculated the secular variation of 0.73 seconds, and from the sinusoidal term, the period variation turned out to be 62.9 years with amplitude of 0d.024. If we assume only the sinusoidal period variation of AB And, the period has to be decreased with 10 years. However if we consider quadratic term with the sinusoidal period variation of the light elements, the period is expected to be increased. Therefore long-term observations of this binary system are required to confirm this issue.