The four-color ( B V R _ { c } I _ { c } ) light curves of V776 Cas are presented and analyzed using the Wilson-Devinney ( W-D ) method .
It is discovered that V776 Cas is an early F-type ( F2V ) overcontact binary with a very high contact degree ( f = 64.6 \% ) and an extremely low mass ratio ( q = 0.130 ) , which indicate that it is at the final evolutionary stage of cool short-period binaries .
The mass of the primary and secondary stars are calculated to be M _ { 1 } = 1.55 ( \pm 0.04 ) M _ { \odot } , M _ { 2 } = 0.20 ( \pm 0.01 ) M _ { \odot } .
V776 Cas is supposed to be formed from an initially detached binary system via the loss of angular momentum due to the magnetic wind .
The initial mass of the present primary and secondary components are calculated to be M _ { 1 i } = 0.86 ( \pm 0.10 ) M _ { \odot } and M _ { 2 i } = 2.13 ( \pm 0.04 ) M _ { \odot } .
The observed-calculated ( O - C ) curve exhibits a cyclic period variation , which is due to the light-travel time effect ( LTTE ) caused by the presence of a third component with a period of 23.7 years .
The mass of the third component is estimated to be M _ { 3 } = 1.04 ( \pm 0.03 ) M _ { \odot } and the orbital inclination of the third component is calculated to be i ^ { \prime } = 33.1 ^ { \circ } .
The distance of the binary system to the mass center of the triple system is calculated to be a ^ { \prime } _ { 12 } = 3.45 AU .
The presence of the close-in tertiary component may play an important role in the formation and evolution of this binary system by drawing angular momentum from the central system .