The Analysis Of Period Changes For The Highamplitude δ Scuti Stars

We analyzed the observed-calculated(O-C) diagrams for four High-amplitude δ Scuti stars, GSC 4464-0924、V524 And、AD CMi and CY Aqr. GSC 4464-0924 is found with period increasing with rate 123.10 10 days/cycle-?. V524 And is found with period decreasing with rate 122.45 10 days/cycle-- ?. The O-C diagrams of AD CMi and CY Aqr present more complex shapes. Therefore, futher anlaysis were done for the two stars. Firstly, the approximate frequency harmonics and amplitudes were recognized by using the discrete Fourier transformation method. Secondly, by using the Kopal’s method, the orbital parameters of the supposed component stars were derived. The solution suggests the existence of one companion star for AD CMi, the period is 26.36 years and eccentricity is 0.8542, the mass of the companion between 1.0228M⊙ and 2.6595M⊙ when the orbit inclination between 30? and 90?. The CY Aqr is very probably in a triple system. The period for the first companion is 54.2 years and eccentricity is 0.49, the mass of the companion between 0.09M⊙ and 0.04M⊙ when the orbit inclination between 30?and 90?. The period for the second companion is 47.3 years and eccentricity is 0.69, the mass of the companion between 0.05M⊙ and 0.02M⊙ when the orbit inclination between 30? and 90?.