Many variable stars have periods that are not stable over time. This tutorial explains the usage of the WWZ Weighted Wavelet Z-Transform method, to study if a period change is present in the light curve of T UMi. This is a member of the semi-regular variables. These are giants or supergiants showing noticeable periodicity in their light changes, accompanied or sometimes interrupted by various irregularities, often indicative of evolutionary changes. 

T UMi is discussed in Grant Foster's book1 "Analyzing Light Curves - A Practical Guide", where he computes periodograms for different time segments of the light curve, and shows that the dominant period changes across the segments.

The observations in this tutorial have been extracted from the AAVSO International Database2.


(1) Published by

(2) We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide, and used in this research.