With most variable stars, a period of variability cannot be measured in a single, night, observation. Vast majority of light curves are derived from a conglomeration of individual measurements that are “Folded” together to create a “Phase Plot”. When the data is successfully folded into a phase plot, each measurement of a particular magnitude is then added to others at increasing period intervals.
Light Curve O-C Diagrams
The O–C (Observed – Computed) method is the classical method for studying period changes in variable stars, because it is sensitive to the cumulative effect of the period changes. O-C diagrams compare the observed time of maximum brightness O with the calculated time...