Phasefolded

Phasefolded refers to a representation of time-series data obtained by folding the data onto a single cycle of a presumed or measured period. The technique is used to reveal periodic signals that may be hidden by noise or by the averaging of many cycles. By aligning data taken at different times that share the same phase in a cycle, a phase-folded plot emphasizes recurrent features and improves signal-to-noise ratio.

The process starts with a time series of measurements and a period P, along with a reference epoch t0. For each observation time t, the phase is computed as φ = ((t − t0) / P) mod 1, producing a phase value in the interval [0, 1). The measurements are then ordered by phase and often binned to create a phase-folded curve. If the period is unknown, the data can be scanned over a range of P values to find the period that yields the most coherent folded profile, a method commonly used in epoch folding and periodogram analyses.

Phase folding is widely used in astronomy, particularly with photometric light curves of variable stars, pulsars, and transiting exoplanets. In pulsar astronomy, phase-folded pulse profiles consolidate many rotations to reveal stable pulse shapes. In exoplanet studies, folding a stellar light curve on the orbital period can reveal faint transit events that recur each orbit. The approach also appears in other time-series analyses where a periodic signal is expected.

Limitations include sensitivity to the accuracy of the assumed period and epoch, potential phase smearing if the period drifts, and uneven sampling or gaps that can distort the folded profile.