ON THE IRREGULAR LIGHT VARIATION OF RU CAMELOPARDALIS

RU Camelopardalis is a W Virginis variable which has light curve with irregularly variable amplitude, mean value and phase. The Fourier-spec trum of the light variation shows a complex structure with the charact eristic period of 22 days. The visual observations before 1960 also sh ow this complex variation, but a dominant regular component was found in these data, too. There are some possible mechanisms underlying the erratic variations of stars: deterministic chaos, stochastic excitatio n and multiperiodicity with unresolved frequencies. In order to choose from these mechanisms we applied different kinds of analyses and nume rical tests. The time-frequency analysis of the light curve indicates that the variation cannot be modelled by a multiperiodic variation. Ph ase-space reconstruction of the data was made in order to prove the ex istence of low dimensional chaos, but the phase portraits do not show any regular structure, i.e. the data cannot be modelled with a low dim ensional (approximately 2 - 3) chaotic system.