Comparison of observational and theoretical parameters for short-period type II Cepheid variables

A comparison is made of observational and theoretical data for short-period Type II Cepheid variable stars. The technique of Fourier decomposition is applied to both a set of observed light curves and a set of theoretical light curves from non-linear hydrodynamical models. Comparison of the variation with period of Fourier parameters for the two sets indicate broad agreement between them, with particular agreement on the abrupt changes which occur near a period of 1.6 days. Linear models are then used to study the fundamental and higher harmonics and to demonstrate the coincidence of this feature with the P2/Po = 0.5 resonance condition. Both linear and non-linear models also enable the construction of period-mass-luminosity-temperature relations, with possibilities for the determination of the masses of these variables