Light variations in V 839 Oph (
,
, 
) were discovered by
Rigollet
(1947), who gave 131 visual estimates and classified the star as
belonging to the type W Ursae Majoris. The first photometric
observations of this system have been made by Binnendijk (1960), who
observed it photoelectrically at two wavelengths, 5300 and 4420 Å with
the 28-inch reflector of the Flower and Cook Observatory in Pennsylvania in
1958 and 1959, and determined three significant minima. It is a pity that
between Rigollet's discovery and Binnendijk's study nobody published
about
this system.
Only one year after Binnendijk's study, Wilson & O'Toole
(1965) observed on one night in 1961 in B and V and
published the data of a secondary minimum, that they had discovered
using observations of one night in 1961. Again many years
(
) passed without any observations until Diethelm (1974a)
started to visually observe it. The visual data however show a large
scatter, although they fill the second big gap between the first group of
photometric data and the photometry of Braune et al. (1981).
The first results on its geometrical and physical elements were obtained by Niarchos (1978) using Kopal's frequency-domain technique and Binnendijk (1960)'s data. More photometric observations of the system were obtained in two wavelenghts (B and V) during the years 1982-1983 by Lafta & Grainger (1985) and analysed using Kopal's frequency-domain technique. They also determined the geometrical and physical elements. Although they present all of the observational data, no times of minima have been computed from their observations and in the present work we have calculated three times of minima using their data. After Lafta & Grainger (1985)'s paper, the same frequency-domain technique was applied on V 839 Oph by Niarchos (1989) (using his own data) and by Al-Naimy et al. (1989).
Other photometric times of minima have been given by Niarchos (1988), Hanžl (1990), Paschke (1990), Hanžl (1991), Hanžl (1994), Agerer & Hübscher (1994) and Demircan et al. (1994a).
No spectroscopic observation have been published for the system. We present new observations of V 839 Oph in U, B and V. Using them, we have investigated the period variation of the system and its probable connection with the light curve variations within the context of mass transfer, magnetic activity, and third body in the system. In addition, this paper presents the light curve solution for V 839 Oph using the Wilson-Devinney (WD) code under the radiative envelope and convective envelope assumptions.