Multi-color ( B V R _ { c } I _ { c } ) CCD photometric light curves of the contact binary V502 Oph are analyzed using the Wilson-Devinney ( W-D ) program .
The solutions reveal that V502 Oph is a W-subtype contact ( f = 35.3 \% ) binary system .
The temperature difference between its two components is 240 K and the more massive star has a lower surface temperature .
A cool spot is added in our model to account for the light curves ’ asymmetry ( O ’ Connell effect ) and third light is detected for the first time in the light curves ’ modeling .
Combining the orbital inclination ( i = 76.4 ^ { \circ } ) with the published mass function of V502 Oph , the absolute physical parameters of the two components are determined , which are M _ { 1 } = 0.46 ( \pm 0.02 ) M _ { \odot } ,M _ { 2 } = 1.37 ( \pm 0.02 ) M _ { \odot } ,R _ { 1 } = 0.94 ( \pm 0.0 % 1 ) R _ { \odot } ,R _ { 2 } = 1.51 ( \pm 0.01 ) R _ { \odot } ,L _ { 1 } = 1.13 ( \pm 0.02 ) L _ { \odot } and L _ { 2 } = 2.49 ( \pm 0.03 ) L _ { \odot } .
The formation and evolutionary status of V502 Oph are discussed .
All photoelectric and CCD times of light minimum about V502 Oph are gathered and its orbital period variations are analyzed .
The results show that the orbital period of V502 Oph is decreasing continuously at a rate of dP / dt = -1.69 \times { 10 ^ { -7 } } day \cdot year ^ { -1 } , which corresponds to a conservative mass transfer rate of \frac { dM _ { 2 } } { dt } = -3.01 \times { 10 ^ { -8 } } M _ { \odot } / year .
The light-travel time effect ( LTTE ) is due to the presence of a close-in tertiary component with a period of P _ { 3 } = 18.7 years and an amplitute of 0.00402days .
V502 Oph is an ideal target to test the formation and evolution theories of binary and multiple systems in which the light curves , O - C curve and spectroscopic observations are comprehensively researched .