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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 : 11 0 7 d =yr. The period increment in- dicates that the conservative mass transfer rate from the less massive component to the more massive one is 6: 51 0 7 M =yr. We tted parabolic and we discuss the possible detection of sinusoidal curves to the (O C) dia- gram and sinusoidal oscillations with period of about 20 yr and semi-amplitude of 0:0065 day. A simultaneous solution of the B and V light curves was computed using the Wilson-Devinney synthetic light- curve code. The light curve solution indicates that the A-type W UMa-type system is in contact with a lling factor of39%.

UBV photometry and period variations of V 839 Ophiuchi