Abstract This dissertation presents time series analysis (TSA) on the simultaneous multichannel photometric observations to study stellar differential rotation with a novel three stage, multichannel period analysis (MPA).

The traditional TSA methods are typically applied only to one channel photometric observations. This PhD work devises a new MPA method, based on the traditional TSA technique, to analyze simultaneously all channel data together. The applications of MPA focus on analyzing the photometric observations of brightness variations of stars, studying stellar surface spottedness and differential rotation. Similarly to the solar differential rotation, which can be studied using sunspots, stellar differential rotation can be investigated from photometric variations caused by surface spots, which can be observed instrumentally and analyzed by different TSA techniques.

The PhD work shows that the MPA method has advantages both in recovering physical periodicities and in achieving higher accuracies of the final results over the traditional TSA applied to the single channel data. It also displays that theMPA method is able to detect the stellar differential rotation from the photometric variability and its applications can help understanding the stellar differential rotation, the magnetic field evolution and the physics of dynamos.