The Conditional Entropy1 (CE) periodogram was introduced by Matthew J. Graham. It is based on the conditional Shannon entropy of a light curve and has the advantage of accounting for systematic effects in the phase space coverage of time series (e.g., gaps). It has comparable performance to other period analysis methods with simulated data, but is superior with real data (observations), both for finding periods and for just identifying periodic behaviour. It is robust against common aliasing issues found with other period analysis methods.

The CE dialog box is similar to the Lomb-Scargle dialog box, but allows to enter Nb (number of phase bins) and Nc (number of mag bins) values in the Additional parameters section. A good general scheme is to use Nb = 5 and Nc = 2 for a first scan of the data. Later on, a finer bin structure (e.g., using Nb = 10 and Nc = 5) can be used to obtain a more accurate period.


Prominent periods of the Period Window appear as valleys.

(1) MNRAS, Vol. 434, Issue 3, 21 Sep 2013, p 2629-2635