The galactic double-mode Cepheids II. Properties of the generalized phase differences

Abstract

By considering the least-squares fits of the double-mode Cepheid light curves discussed in Paper I we defined their properties by their Fourier parameters and generalized phase differences $G_{i,j}$. When plotting the latter quantities as a function of the respective order, the second order terms are confined in the region just below 3/2$π$; the third order terms have $π/2 < G_{i,j} < π$, the fourth order ones cluster around 2$π$ (or 0), the fifth order ones seem to have $π< G_{i,j} < 3/2 π$. The mean $G_{i,j}$ values are also regularly spaced. The progression of the $G_{i,j}$ values as a function of the period was investigated and the signature of a possible resonance near 6.0 d was found.