Phase-folding methods

class periodicity.phase.PDM(nb=5, nc=2, p_min=None, p_max=None, n_periods=1000, oversample=1, do_subharmonic=False, cores=None)

Bases: object

Phase Dispersion Minimization 1.

Parameters

  • nb (int, optional) – Number of phase bins (the default is 5).

  • nc (int, optional) – Number of covers per bin (the default is 2).

  • p_min (float, optional) – Minimum/maximum trial period.

  • p_max (float, optional) – Minimum/maximum trial period.

  • n_periods (int, optional) – Number of trial periods (the default is 1000).

  • oversample (scalar, optional) – If p_max is omitted, the time baseline multiplied by oversample will be used instead.

  • do_subharmonic (bool, optional) – Whether to perform subharmonic averaging. This option looks for a significant minimum in \(\theta\) at both the main period and its double. For actual variations, both will be present. For a noise result, the double period signal will not be present.

  • cores (int, optional) – The number of parallel cores to use. By default it will try to use all available CPU cores.

References

1

R. F. Stellingwerf, “Period determination using phase dispersion minimization,” ApJ, September 1978.

2

R. F. Stellingwerf, “Period Determination of RR Lyrae Stars,” RR Lyrae Stars, Metal-Poor Stars and the Galaxy, August 2011.

_pdm(period)

Calculates the PDM theta statistic for a single trial period.

class periodicity.phase.StringLength(dphi=0.1, n_periods=1000, cores=None)

Bases: object

String Length 2.

Parameters

  • dphi (float, optional) – Factor to multiply (1 / baseline) in order to get the frequency separation (the default is 0.1).

  • n_periods (int, optional) – Number of trial periods (the default is 1000).

  • cores (int, optional) – The number of parallel cores to use. By default it will try to use all available CPU cores.

References

3

M. M. Dworetsky, “A period-finding method for sparse randomly spaced observations or ‘How long is a piece of string ?’,” MNRAS, June 1983.

_stringlength(period)

Calculates the string length for a single trial period.

References and additional reading