Period variation study of the a-type W UMa eclipsing binary V839 Oph

We present an analysis of the measurements of mid-eclipse times of V839 Oph, collected from literature sources. Our analysis indicates a period increase of 3:2 × 10-7 day/yr. This period increase of V839 Oph can be interpreted in terms of mass transfer of rate 1.76 × 10-7M⊙/yr, from the less to the more massive component. The O - C diagram shows a damping sine wave covering two different complete cycles of 36.73 yr and 19.93 yr with amplitudes approximately equal to 0:0080 and 0:0043 day, respectively. The third cycle has to be expected to cover about 13.5 years with lower amplitude than those of the former two cycles. These unequal duration cycles show a non periodicity which may be explained as resulting from either the presence of a tertiary component to the system or cyclic magnetic activity variations due to star spots. For the later mechanism, the obtained characteristics are consistent when applying Applegate (1992) mechanism. © 2010 The Korean Astronomical Society. All Rights Reserved.