UBV PHOTOMETRY AND PERIOD VARIATIONS OF V-839-OPHIUCHI

A complete period variation analysis and new light curves of V 839 Oph together with new ephemeris data are presented. The period variation was found to be dP/dt = 3.1 10(-7) d/yr. The period increment indicate s that the conservative mass transfer rate from the less massive compo nent to the more massive one is 6.5 10(-7) M./yr. We fitted parabolic and we discuss the possible detection of sinusoidal curves to the (O-C ) diagram and sinusoidal oscillations with period of about 20 yr and s emi-amplitude of 0.0065 day. A simultaneous solution of the B and V li ght curves was computed using the Wilson-Devinney synthetic lightcurve code. The light curve solution indicates that the A-type W UMa-type s ystem is in contact with a filling factor of similar to 39%.