Exploring Timescales Among Those Other Variables

The timescale of variability among periodic variables can be characterized by
a single value, the period. The availability of standard methods to measure
the period of a light curve has made possible a wealth of studies on
everything from near-Earth asteroids to the cosmic distance scale. However,
many variable sources, including active galactic nuclei, chaotic pulsators,
and accreting stars, are not even approximately periodic. Can we identify a
single number that can fill the same role for aperiodic variables as the
period does for periodic variables? Here, I present my first steps toward
addressing this question, using a combination of theoretical and empirical
work from the PTF North America Nebula (PTF-NAN) survey and the Young Stellar
Object Variability (YSOVAR) project.