PERIOD VARIATION STUDY OF THE A-TYPE W UMA ECLIPSING BINARY

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