Pseudo Periodic Signal
Due the extreme low SNR of observations of millions of new stars with new satellite telescopes, plotting the motion and distance of new stars by the pulsing periods of faint light, the wavelength shifts and the phase, many periods are unknown or not exactly or just sometimes periodic hence pseudo-periodic.
There are many gravitational influences to consider such as the attraction forces of black holes and the centripetal forces of possible planets.  It has been found on our solar system that moons are phase and frequency locked to the planet’s rotational frequency such that the only one side of the moon is visible from the surface if they rotate at the same fundamental frequency. It is known that there are over 200 moons in our planetary system and many are retrograde and have become synchronous to the hosting planet’s rotational frequency by x1 like earth is moon, or 1x,2x, 4x. Many are not perfect orbits and the mass of the moon can wobble a distant planet’s orbit, just as Uranus, the largest planet is almost synchronized to the solar flare 11 yr cycle, which also have many longer cycles up to thousands of years suggesting how solar flares are modulated in their eruptions by external forces. This is an example how distant stars can be modulated in their emissions. It is far more complex than simply Keppler’s Law.
Once the mechanism of the modulations are discovered, then the periodic emissions of stars can be understood, or visa versa by simulated models, such as which ones might inhabit an earth like planet with an exquisite balance of energy to support life with cycles of temperature that are near 0’C to sustain  all the other cycles of life, water content and gas cycles from plants.  The stability of nature has so many exponential powers of balance, it is even far greater than the stability of an atomic clock. Yet modulation in climate change from atomic to organic to atmospheric to chemical to laws of physics that predicting the consequences of disturbances is a major concern by scientists in each field. It is so complex that divergent opinions exist on climate change that warming and cooling exponential and pseudo-periodic and periodic functions exist increase the apparent modulation of temperature extremes that can cause polar ice to melt at alarming rates with snow in Texas in the spring and conflicting theories about carbon cycles.
There are possibly many fields of science explored with pseudo-periodic functions like Schumann resonance of the magnetosphere that are impulse triggered by solar X flares and the global consciousness of similar emitted brain wave cycles as well as the known diurnal effects of light.