This was done based on the well-known framework of O-C diagrams. The obtained O-C diagram already showed that AU Peg is indeed not a regular star, with the shape of the diagram being strongly distorted compared to the normally expected parabole.
AU Pegasi revisited: period evolution of a peculiar Type II Cepheid
Content overview (TL;DR)
This short paper dealt with the peculiar behaviour of a not-so-well-studied Type II Cepheid, which is among the shortest-period binaries of its class (with an astonishingly short orbital period of 53.3 days). Previously, it was found that this Cepheid exhibits a somewhat erratic pulsation period change, with the period settling on a value for a while at times, then starting to increase with significant acceleration at some point. The main goal of this subproject was to extend and re-analyze the photometric data obtained for this variable to see how its pulsation period evolved over the years.
Based on this diagram, the pulsation period evolution of the variable could be drawn, which turned out to be non-linear and erratic. It is also apparent that the change in the period is pretty significant; the star's pulsation period changed by _percents_ over human timescales!
