Multi-color light curves of V1197 Her were obtained with the 2.4 meter optical telescope at Thai National Observatory and the Wilson-Devinney ( W-D ) program is used to model the observational light curves .
The photometric solutions reveal that V1197 Her is a W-subtype shallow contact binary system with a mass ratio of q = 2.61 and fill-out factor to be f = 15.7 \% .
The temperature difference between the primary star and secondary star is only 140 K in spite of the low degree of contact , which means that V1197 Her is not only in geometrical contact configuration but also already under thermal contact status .
The orbital inclination of V1197 Her is as high as i = 82.7 ^ { \circ } , and the primary star is completely eclipsed at the primary minimum .
The totally eclipsing characteristic implies that the determined physical parameters are highly reliable .
The masses , radii and luminosities of the primary star ( star 1 ) and secondary star ( star 2 ) are estimated to be M _ { 1 } = 0.30 ( 1 ) M _ { \odot } , M _ { 2 } = 0.77 ( 2 ) M _ { \odot } , R _ { 1 } = 0.54 ( 1 ) R _ { \odot } , R _ { 2 } = 0.83 ( 1 ) R _ { \odot } , L _ { 1 } = 0.18 ( 1 ) L _ { \odot } and L _ { 2 } = 0.38 ( 1 ) L _ { \odot } .
The evolutionary status of the two component stars are drawn in the H - R diagram , which shows that the less massive but hotter primary star is more evolved than the secondary star .
The period of V1197 Her is decreasing continuously at a rate of dP / dt = -2.58 \times { 10 ^ { -7 } } day \cdot year ^ { -1 } , which can be explained by mass transfer from the more massive star to the less massive one with a rate of \frac { dM _ { 2 } } { dt } = -1.61 \times { 10 ^ { -7 } } M _ { \odot } / year .
The light curves of V1197 Her is reported to have the O ’ Connell effect .
Thus , a cool spot is added to the massive star to model the asymmetry on light curves .